Merge "Improve error handling when nvp and quantum are out of sync"

diff --cc quantum/plugins/nicira/nicira_nvp_plugin/QuantumPlugin.py
Simple merge

diff --cc quantum/tests/unit/nicira/test_nicira_plugin.py
index d5c527836ead5777b5a246cd5fb2e412f2060d4e,f96b4bfe1a433911dcd7ae4de00c9871f824fc51..d567053f3de945ac6df648f78b3ce66eb664f6e0
--- 1/quantum/tests/unit/nicira/test_nicira_plugin.py
--- 2/quantum/tests/unit/nicira/test_nicira_plugin.py
+++ b/quantum/tests/unit/nicira/test_nicira_plugin.py
@@@ -19,9 -19,9 +19,10 @@@ import o
  
  import mock
  from oslo.config import cfg
 +import netaddr
  import webob.exc
  
+ from quantum.common import constants
  import quantum.common.test_lib as test_lib
  from quantum import context
  from quantum.extensions import providernet as pnet