Fix: libcrmservices: Add another place to finalize Start/Stop ops

The comment should explain this pretty well. What was happening was that
an executor regression test was failing because the operation never gets
finalized. Essentially, services__finalize_async_op() never gets called
for a unit that doesn't exist.

We typically want this to happen as part of the systemd callback that's
registered in the executor, but this callback will never get called in
this case because there's no systemd message that will make it through
our filter and trigger the callback. JobRemoved won't get sent because
there's no job to remove.

It seems like we could look for a failure from LoadUnit for units that
don't exist, but pacemaker always writes an override unit file which
means the unit will always exist.