remove default=None for config options

In the cfg module default=None is set as the default value.

Change-Id: I235decf26827bcb8076867f63c005ce5a80554fa
diff --git a/tempest/config.py b/tempest/config.py
index 0796d98..0fb3fd3 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -40,7 +40,6 @@
                 default=False,
                 help="Set to True if using self-signed SSL certificates."),
     cfg.StrOpt('uri',
-               default=None,
                help="Full URI of the OpenStack Identity API (Keystone), v2"),
     cfg.StrOpt('uri_v3',
                help='Full URI of the OpenStack Identity API (Keystone), v3'),
@@ -60,52 +59,40 @@
                         'publicURL', 'adminURL', 'internalURL'],
                help="The endpoint type to use for the identity service."),
     cfg.StrOpt('username',
-               default=None,
                help="Username to use for Nova API requests."),
     cfg.StrOpt('tenant_name',
-               default=None,
                help="Tenant name to use for Nova API requests."),
     cfg.StrOpt('admin_role',
                default='admin',
                help="Role required to administrate keystone."),
     cfg.StrOpt('password',
-               default=None,
                help="API key to use when authenticating.",
                secret=True),
     cfg.StrOpt('domain_name',
-               default=None,
                help="Domain name for authentication (Keystone V3)."
                     "The same domain applies to user and project"),
     cfg.StrOpt('alt_username',
-               default=None,
                help="Username of alternate user to use for Nova API "
                     "requests."),
     cfg.StrOpt('alt_tenant_name',
-               default=None,
                help="Alternate user's Tenant name to use for Nova API "
                     "requests."),
     cfg.StrOpt('alt_password',
-               default=None,
                help="API key to use when authenticating as alternate user.",
                secret=True),
     cfg.StrOpt('alt_domain_name',
-               default=None,
                help="Alternate domain name for authentication (Keystone V3)."
                     "The same domain applies to user and project"),
     cfg.StrOpt('admin_username',
-               default=None,
                help="Administrative Username to use for "
                     "Keystone API requests."),
     cfg.StrOpt('admin_tenant_name',
-               default=None,
                help="Administrative Tenant name to use for Keystone API "
                     "requests."),
     cfg.StrOpt('admin_password',
-               default=None,
                help="API key to use when authenticating as admin.",
                secret=True),
     cfg.StrOpt('admin_domain_name',
-               default=None,
                help="Admin domain name for authentication (Keystone V3)."
                     "The same domain applies to user and project"),
 ]
@@ -234,7 +221,6 @@
                default='computev3',
                help="Catalog type of the Compute v3 service."),
     cfg.StrOpt('path_to_private_key',
-               default=None,
                help="Path to a private key file for SSH access to remote "
                     "hosts"),
     cfg.StrOpt('volume_device_name',
@@ -323,18 +309,14 @@
 
 ComputeAdminGroup = [
     cfg.StrOpt('username',
-               default=None,
                help="Administrative Username to use for Nova API requests."),
     cfg.StrOpt('tenant_name',
-               default=None,
                help="Administrative Tenant name to use for Nova API "
                     "requests."),
     cfg.StrOpt('password',
-               default=None,
                help="API key to use when authenticating as admin.",
                secret=True),
     cfg.StrOpt('domain_name',
-               default=None,
                help="Domain name for authentication as admin (Keystone V3)."
                     "The same domain applies to user and project"),
 ]
@@ -653,11 +635,9 @@
                help="Instance type for tests. Needs to be big enough for a "
                     "full OS plus the test workload"),
     cfg.StrOpt('image_ref',
-               default=None,
                help="Name of heat-cfntools enabled image to use when "
                     "launching test instances."),
     cfg.StrOpt('keypair_name',
-               default=None,
                help="Name of existing keypair to launch servers with."),
     cfg.IntOpt('max_template_size',
                default=524288,
@@ -726,11 +706,9 @@
                default="http://localhost:8080",
                help="S3 URL"),
     cfg.StrOpt('aws_secret',
-               default=None,
                help="AWS Secret Key",
                secret=True),
     cfg.StrOpt('aws_access',
-               default=None,
                help="AWS Access Key"),
     cfg.StrOpt('aws_zone',
                default="nova",
@@ -769,26 +747,20 @@
 
 StressGroup = [
     cfg.StrOpt('nova_logdir',
-               default=None,
                help='Directory containing log files on the compute nodes'),
     cfg.IntOpt('max_instances',
                default=16,
                help='Maximum number of instances to create during test.'),
     cfg.StrOpt('controller',
-               default=None,
                help='Controller host.'),
     # new stress options
     cfg.StrOpt('target_controller',
-               default=None,
                help='Controller host.'),
     cfg.StrOpt('target_ssh_user',
-               default=None,
                help='ssh user.'),
     cfg.StrOpt('target_private_key_path',
-               default=None,
                help='Path to private key.'),
     cfg.StrOpt('target_logfiles',
-               default=None,
                help='regexp for list of log files.'),
     cfg.IntOpt('log_check_interval',
                default=60,