The libxlDomainMigrationSrc* functions are a bit flawed in their
handling of modify jobs. A job begins at the start of the begin
phase but ends before the phase completes. No job is running for
the remaining phases of migration on the source host.

Change the logic to keep the job running after a successful begin
phase, and end the job in the confirm phase. The job must also end
in the perform phase in the case of error since confirm phase would
not be executed.
Signed-off-by: NJim Fehlig <jfehlig@suse.com>
ACKed-by: NMichal Privoznik <mprivozn@redhat.com>