Add integration scenario test for Neutron LBaaS

- added new scenario test that checks work of Neutron LBaaS resource:
test creates stack with two servers and LB resource, checks connection,
adds one more member to LP and finally checks load balancing.

Co-Authored-by: Sergey Kraynev <skraynev@mirantis.com>

Change-Id: I5d05909d437a2ba7b047ae758f3b5d8669fc8b1b
diff --git a/common/config.py b/common/config.py
index 878cd33..158d087 100644
--- a/common/config.py
+++ b/common/config.py
@@ -103,6 +103,10 @@
     cfg.BoolOpt('skip_stack_abandon_tests',
                 default=False,
                 help="Skip Stack Abandon Integration tests"),
+    cfg.IntOpt('connectivity_timeout',
+               default=120,
+               help="Timeout in seconds to wait for connectivity to "
+                    "server."),
 ]