This partially reverts 82592551.

When migrating a domain, qemuMigrationDstPrepareAny() is called
which eventually calls qemuProcessLaunch(conn = NULL, flags =
VIR_QEMU_PROCESS_START_AUTODESTROY); But the very first thing
that qemuProcessLaunch does is check if AUTODESTROY flag is set
and @conn is not NULL. Well, it is.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>