migration: allow src return path to pause

Let the thread pause for network issues.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180502104740.12123-6-peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
3 files changed