qemuProcessHandleMigrationStatus: Update migration status more frequently
    
    After Jirka's migration patches libvirt is listening on migration
    events from qemu instead of actively polling on the monitor. There is,
    however, a little regression (introduced in 6d2edb6a42d0d41). The
    problem is, the current status of migration job is updated in
    qemuProcessHandleMigrationStatus if and only if migration job was
    started. But eventually every asynchronous job may result in
    migration. Therefore, since this job is not strictly a
    migration job, internal state was not updated and later checks failed:
    
      virsh # save fedora22 /tmp/fedora22_ble.save
      error: Failed to save domain fedora22 to /tmp/fedora22_ble.save
      error: operation failed: domain save job: is not active
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>