Use realm specific filename with mwversionsinuse

When mwversionsinuse was ported from shell to python it incorrectly
omitted using the PHP realm specific filename logic when opening the
wikiversions.json file. In beta the wikiversions-labs.json file should
be used rather than the wikiversions.json file which is production
configuration.

Bug: 62262
Change-Id: Id401f7ccf7b293617b14414efa6de07834b10e8e
Replace cluster_monitor with a ssh.Job class

Convert simplistic ssh.cluster_monitor function into the ssh.Job class
which allows running a remote command to be progressively described
using syntax that makes the intent of the final operation more clear to
readers.

The new log.ProgressReporter class can be used to display progress
messages for cluster_ssh or other multi-step tasks that have a concept
of success, failure and steps to be performed.

Change-Id: I5580e3a520aac8126b569188844c7aa5db3a93d6
Remove scap.tasks.scap

Move the business logic previously contained in scap.tasks.scap to the
scap.main.Scap class.

Change-Id: I848cd213327052b2b1c4774ae5f5e375febc3643