Clean-up in the unit tests for NVP plugin

Simplify and reduce duplication in the unit test framework
for the NVP plugin.

Fixes bug 1204694

Change-Id: Ia96e1c2386ac013c24a2c7716d0e97ea6fdcf5d1
Update to latest oslo rootwrap

Update Neutron rootwrap to the latest from oslo-incubator. This allows
to get rid of the DnsMasqFilter (which was already replaced by
EnvFilter) in preparation for the havana release, as well as get a few
bugfixes.

All the changes are coming directly from the Oslo "rootwrap" module
sync.

Change-Id: Ic373710cce0716323f4349414bb5b231f48d9177
Imported Translations from Transifex

Change-Id: I2ea5d3340d3c5cd3baf901c31252375aff4c2a1f
Merge "Clean-up in the unit tests for NVP plugin"
Merge "Update to latest oslo rootwrap"