commit b9d934f2 upstream.

After a resume the hypervisor/tools may change console event
channel number. We should re-query it.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>