VMware: Network fallback in case specified one not found

In the case that opqaue network does not match the bridge ID then
we will fall back on a predefined network (configurable by the admin
via 'integration_bridge' in the 'vmware' section).

Fixes bug 1225002

(cherry picked from commit a0546fd3f42c37e8cd6e4e9b70d59ae1e689b4b7)

Conflicts:

	nova/tests/test_vmwareapi_vif.py
	nova/virt/vmwareapi/vif.py

Change-Id: Idd28986aac12461754194d3fdd04004748a14893
Merge "VMware: Network fallback in case specified one not found" into stable/grizzly