qemuMigrationFetchJobStatus is rather inconvinient. Some of its
callers don't need status to be updated, some don't need to update
elapsed time right away. So let's update status or elapsed time
in callers instead.

This patch drops updating job status on getting job stats by
client. This way we will not provide status 'completed' while
it is not yet updated by migration routine.
Signed-off-by: NJiri Denemark <jdenemar@redhat.com>