Add functional tests for Manila consistency groups

This commit adds tempest functional tests for Manila consistency
groups and cgsnapshot objects and actions. By default these tests are
enabled; 3rd party CI systems should disabled these tests through the
RUN_MANILA_CG_TESTS environment variable if their driver does not
support consistency groups.

Partially implements bp manila-consistency-groups
Change-Id: I3297e02ad53c328f0bfe5245fefdb6af80552b4a
diff --git a/manila_tempest_tests/config.py b/manila_tempest_tests/config.py
index 2c5e809..046f8cd 100644
--- a/manila_tempest_tests/config.py
+++ b/manila_tempest_tests/config.py
@@ -139,6 +139,11 @@
                 help="Defines whether to run tests that use share snapshots "
                      "or not. Disable this feature if used driver doesn't "
                      "support it."),
+    cfg.BoolOpt("run_consistency_group_tests",
+                default=True,
+                help="Defines whether to run consistency group tests or not. "
+                     "Disable this feature if used driver doesn't support "
+                     "it."),
     cfg.StrOpt("image_with_share_tools",
                default="manila-service-image",
                help="Image name for vm booting with nfs/smb clients tool."),