Add grenade-dsvm-partial-ncpu test

Add support for grenade based partial upgrade test. Since the partial
upgrade test only supports nova-compute, this job is added to just nova.
Set to non-voting for now with the goal of making this voting once we
get comfortable with it.

Change-Id: Ic680502d4dcc0a8677749bc38bf57b6c76c881f7
Merge "Add grenade-dsvm-partial-ncpu test"