Allow staging builds after a production hot fix

Hot fixes change YYYY.MM to YYYY.MM.X where X is
an incrementing number. This causes staging builds
after the hot fix to be lower than the builds before
the fix. Drop the increment and use the time.day
field to increment staging builds.

Change-Id: I5af730ee58e6f1044b2dbb1d51c8f05ee8fdf5e6