[RBAC] Add skip condition for share manage

In case a backend doesn't support this feature
the tests will fail.

Change-Id: I69fd7a3747986ce287c3a59cdc0f374fdd5b0099
diff --git a/manila_tempest_tests/tests/rbac/test_share_manage.py b/manila_tempest_tests/tests/rbac/test_share_manage.py
index 6127755..272ec66 100644
--- a/manila_tempest_tests/tests/rbac/test_share_manage.py
+++ b/manila_tempest_tests/tests/rbac/test_share_manage.py
@@ -34,6 +34,8 @@
     @classmethod
     def skip_checks(cls):
         super(ShareRbacManageShareTests, cls).skip_checks()
+        if not CONF.share.run_manage_unmanage_tests:
+            raise cls.skipException('Manage/unmanage tests are disabled.')
         if cls.protocol not in CONF.share.enable_protocols:
             message = "%s tests are disabled" % cls.protocol
             raise cls.skipException(message)