Add support for multiple RPC workers under Metaplugin

Metaplugin needs a fix to support multiple RPC workers properly
because a plugin which supports multiple RPC workers cannot
initialize RPC connections at plugin initialization.

Closes-Bug: #1300570
Change-Id: I584f70abb8969054cd4edc8f914d00f6be930bab
Improved quota error message

Removed two negatives and showed a clear message when
tried to see quota of different tenants.
When a user who does not belong to a project tries to access the
quota of that project, the message that gets displayed is not clear.
In this change the user would understand the error more properly.

Change-Id: I2284df07687bb530fe06fbaab38e2971826b7b40
Closes-Bug: #1288915
Nuage Plugin: Delete router requires precommit checks

There exist a case where deleting router from neutron without
deleting router-interface deletes router from VSD but not from neutron.
If router has an interface with subnet router deletion is not allowed.
Needs to precheck this condition before deleting router from
backend (VSD).

Change-Id: I4ba7eff399acda0427505328355dbfb931d62587
Closes-Bug: #1298635
Merge "Add support for multiple RPC workers under Metaplugin"
Merge "Nuage Plugin: Delete router requires precommit checks"
Merge "Improved quota error message"