Added TAP_DEVICE_PREFIX info to common/constants

Change-Id: Ia84629732490585164237ca4f7d1db90bde9fbf2
Closes-Bug: 1361573
Use dict_extend_functions to populate provider network attributes

Use dict_extend_functions mechanism to handle populating additional
provider network attributes into Network model in Nuage plugin.

Change-Id: I72e5afe3d03ae223fcd8e75f1f4f07624c3a7daf
Closes-Bug: #1362308
Mock out all RPC calls with a fixture

Mock out the rpc proxy calls used by various agents to
prevent unit tests from blocking for 10+ seconds while waiting
for a timeout. This happened with the OVS agent unit tests
recently in Change-ID Idd770a85a9eabff112d9613e75d8bb524020234a.

This change results in a reduction from 330.8 seconds to 2.7 seconds
for the neutron.tests.unit.openvswitch.test_ovs_neutron_agent
test module.

Closes-Bug: #1372076
Change-Id: I5e6794dc33c64c8fe309d8e72a8af3385c7d4442
Merge "Added TAP_DEVICE_PREFIX info to common/constants"
Merge "Mock out all RPC calls with a fixture"
Merge "Use dict_extend_functions to populate provider network attributes"
Merge branch 'master' of https://github.com/openstack/quantum