iotests.py: rewrite run_job to be pickier

iotests.py: rewrite run_job to be pickier

Don't pull events out of the queue that don't belong to us;
be choosier so that we can use this method to drive jobs that
were launched by transactions that may have more jobs.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20190523170643.20794-5-jsnow@redhat.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
(cherry picked from commit d6a79af0e641806d6bd6a42a4920e294b5db179c)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>