qa/suites/upgrade: ignore MON_DOWN and PG_AVAILABILITY warnings in upgrade tests

qa/suites/upgrade: ignore MON_DOWN and PG_AVAILABILITY warnings in upgrade tests

Signed-off-by: Laura Flores <lflores@ibm.com>
(cherry picked from commit e225b127eaf5375493bc1a667058de092f10e4dd)
Signed-off-by: Laura Flores <lflores@ibm.com>
Conflicts:
        qa/suites/upgrade/octopus-x/stress-split/1-start.yaml
	qa/suites/upgrade/quincy-x/parallel/1-tasks.yaml
   - octopus-x/stress-split didn't have an override section yet, while
     main already did. So, I had to add a new section and remove stuff other
     warnings (such as OSD_DOWN) that are out of scope for this cherry-pick.
   - quincy-x tests do not exist on the quincy branch, so I had to remove these
     from the cherry-pick modifications.