Specialize the grenade-multinode job and test the variations
on upgrade where a few services are available on the subnode only
(c-bak only, c-bak+c-vol, c-bak+c-sch+c-vol).
Also, use grenade instead of grenade-py3. The former is now used
(after Iea355514ec7cc2a52ed5e88c356bcb1cdeadd639) in
integrated-gate-storage instead of the latter, which means
that we need to change it in order to apply the value of
irrelevant-files.
Depends-On: https://review.opendev.org/548936
Change-Id: I3eac1afcbb69e25e9b2a916910caf3291aa7c1fe
6c1e52cefc