Install neutron-plugin-ml2 package on Ubuntu

While there is no dedicated package for neutron-plugin-ml2 on Debian,
there is one on Ubuntu operating systems.

We should install it when ML2 core plugin is enabled.

Closes-bug: #1337988
Change-Id: I8ee2bca21cc3f32c017529b55c92a50094aa25d5
for OVS agent, fix dependency on service

Previously, the declaration for vs_bridge required the service, but if
the service is not enabled it's not declared.  This moves the dependency
inside an if.  See bug #1298146 for the background.

Change-Id: Ic51efb16d4ba0a971178ff648f963c61b2e9fdde
Closes-Bug: #1337733
Rename QUOTAS section for quotas

Quotas section in neutron.conf was renamed from [QUOTAS]
to [quotas] in Havana.

Closes-bug: #1341657
Change-Id: I757a804ac846cc96a80bd76994d274b890885625
Merge "Rename QUOTAS section for quotas"
Merge "for OVS agent, fix dependency on service"
Merge "Install neutron-plugin-ml2 package on Ubuntu"