Fix RPM-level upgrades

I have an rpm-upgrade test that I think does a pretty good job of verifying RPM-level ODL upgrades work.

JankiChhatbar has a patch to the RPM spec file to not remove the snapshot and journel dirs during RPM upgrades.

We no longer have the ability to short-term-host RPMs on Jenkins after sandbox build jobs, which is what the "give me two URLs and I'll do the upgrade testing" API of the rpm-upgrade-master test assumes. We'd need to raise a different issue to track making build-rpm jobs run in the sandbox host RPMs on Jenkins while jobs run in the releng Jenkins silo push to Nexus. I've looked at this some and talked with zxiiro a bit and it seemed pretty non-trivial.

Need to revisit the patch, retest it. May need to verify locally for now, following something like the pattern outlined in the upgrade test.

Imported from: https://trello.com/c/z8EAEqso/538-dont-nuke-snapshots-journal-dirs-during-rpm-upgrade