Do not use env var conf defaults

Falling back to environment variable credentials is convenient for
development but could lead to unexpected credentials being used during
tests. Also this is not a known practice for tempest tests.

This change removes the env var defaults and explicitly sets the
credentials to use in prepare_test_env.sh.

Pre and post grenade tests also get their config from the conf file
rather than the environment.

blueprint tempest-plugin-support

Change-Id: Icf9fb4c58ed11483106c2b62d1e1093223f7dc51
diff --git a/common/config.py b/common/config.py
index c2aac65..8081282 100644
--- a/common/config.py
+++ b/common/config.py
@@ -35,10 +35,8 @@
                default="orchestration",
                help="Catalog type of the orchestration service."),
     cfg.StrOpt('username',
-               default=os.environ.get('OS_USERNAME'),
                help="Username to use for non admin API requests."),
     cfg.StrOpt('password',
-               default=os.environ.get('OS_PASSWORD'),
                help="Non admin API key to use when authenticating.",
                secret=True),
     cfg.StrOpt('admin_username',
@@ -47,25 +45,19 @@
                help="Admin API key to use when authentication.",
                secret=True),
     cfg.StrOpt('tenant_name',
-               default=(os.environ.get('OS_PROJECT_NAME') or
-                        os.environ.get('OS_TENANT_NAME')),
                help="Tenant name to use for API requests."),
     cfg.StrOpt('admin_tenant_name',
                default='admin',
                help="Admin tenant name to use for admin API requests."),
     cfg.StrOpt('auth_url',
-               default=os.environ.get('OS_AUTH_URL'),
                help="Full URI of the OpenStack Identity API (Keystone)"),
     cfg.StrOpt('user_domain_name',
-               default=os.environ.get('OS_USER_DOMAIN_NAME'),
                help="User domain name, if keystone v3 auth_url"
                     "is used"),
     cfg.StrOpt('project_domain_name',
-               default=os.environ.get('OS_PROJECT_DOMAIN_NAME'),
                help="Project domain name, if keystone v3 auth_url"
                     "is used"),
     cfg.StrOpt('region',
-               default=os.environ.get('OS_REGION_NAME'),
                help="The region name to use"),
     cfg.StrOpt('instance_type',
                help="Instance type for tests. Needs to be big enough for a "