Some fixes uncovered during v2021.2 stable release branching

Cleanups on OBS can be tricky at times, especially when OBS is busy. THis results in reprepro not being able to run because of already acquired lock. And overriding the lock is highly discouraged.

This change breaks the cleanup into OBS and reprepro separately, to ease the overall workflow

Also extend the help about how the script should be invoked.

Signed-off-by: Ritesh Raj Sarraf ritesh.sarraf@collabora.com