Normally virt-viewer relies on the VNC/SPICE widget seeing
an EOF on its underlying connection to detect when the
session is closed.

When tunnelling to a remote guest over SSH though, this
EOF can be delayed for a very long time, leaving a dead
session open.

This can be seen with

   virt-viewer -c qemu+ssh://remotehost/system

 guestname

when on the remote shell run

   virsh destroy guestname

and notice that virt-viewer does not see the shutdown
immediately.

When we get a domain stopped event we know the session
should be dead, so forceably close it, if not already
closed.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit a62827d2)