Fix neutron func job to install neutron and deps

The neutron functional job wasn't installing neutron, which meant the
sudo config necessary to run the job was not available.  It is also
necessary to have devstack install testonly dependencies to ensure that
functional tests can support the same dependencies as the unit tests.

Change-Id: Iee212995f4c27d55466c753ddca6aace4ffcf35e
Partial-bug: #1336172
Merge "Fix neutron func job to install neutron and deps"