Add test to attach and detach policies with regular client

The test validates that a regular client is allowed to attach\detach
QoS policies only to\from networks with policies that were configured
as "Shared".

This test will not be running automatically because of the creation
of a "Shared" resource during the test.
Setting the create_shared_resources option as 'True' in the config.py
file is needed.

Change-Id: Iec3fda32cbce00a677cb30dac3c234c99d7c27fd
diff --git a/neutron_tempest_plugin/config.py b/neutron_tempest_plugin/config.py
index 54dc16e..51fbafc 100644
--- a/neutron_tempest_plugin/config.py
+++ b/neutron_tempest_plugin/config.py
@@ -115,6 +115,14 @@
                help='Name of ssh user to use with advanced image in tests. '
                     'This is required if advanced image has to be used in '
                     'tests.'),
+
+    # Option for creating QoS policies configures as "shared".
+    # The default is false in order to prevent undesired usage
+    # while testing in parallel.
+    cfg.BoolOpt('create_shared_resources',
+                default=False,
+                help='Allow creation of shared resources.'
+                     'The default value is false.'),
 ]
 
 # TODO(amuller): Redo configuration options registration as part of the planned