Server Manager : fix pylint errors

Change-Id: I70bc885ba42f87b82e0efe0bc5b30f8b0ecafb4a
Partial-Bug: #1389089
server-manager show tag, doesn't work complaining select key error

Change-Id: I80748386e9ecbc3548ed1d51b3f196120f29bd5e
Image category is not storted in the server db

Change-Id: I9b981f15cf61427bafc077f90151e12defba193a
Implementing comments on previous checkin
Merge remote-tracking branch 'upstream/master' into monitoring_cli_move