Verify update plus rebuild

Created by: eli-schwartz

Perform safety checks to verify that there isn't a testing/staging rebuild in progress which will be invalidated by a db-update. This protects against the case where a Dev/TU performs a global rebuild that touches one package in staging, and then another (the original maintainer, say) tries to update the same package but does not realize it needs to be updated for staging as well.

Also make the testing2x script slightly more useful by handling multiple testing repos. The current script was basically written with packages.git in mind alone.