task: update the message when running jobs

Before this patch the message reported by a task was left to "Task
is initializing" for all the execution time.
This patch updates the message reporting what job of the task is
currently running.

Change-Id: I14983c3cf0a394e01173c31e676bebb14041fcd2
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/26773
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Saggi Mizrahi <smizrahi@redhat.com>