Add a functional test option to skip notification tests

When running a standalone heat this can never pass.

Change-Id: Ibf435d6bec241904ada86d5786d69e7618adc13f
diff --git a/common/config.py b/common/config.py
index 0de6480..fd44075 100644
--- a/common/config.py
+++ b/common/config.py
@@ -105,6 +105,9 @@
     cfg.BoolOpt('skip_stack_abandon_tests',
                 default=False,
                 help="Skip Stack Abandon Integration tests"),
+    cfg.BoolOpt('skip_notification_tests',
+                default=False,
+                help="Skip Notification Integration tests"),
     cfg.IntOpt('connectivity_timeout',
                default=120,
                help="Timeout in seconds to wait for connectivity to "