virsh: Allow graceful console shutdown

virsh: Allow graceful console shutdown

Currently, whenever there's a regular EOF on the console stream
or an error the virStreamAbort() is called regardless. While this
may not actually break anything, we should call virStreamFinish()
to let the daemon know we've successfully received all the data
and are shutting down the stream gracefully.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>