ui: remove 'sync' parameter from vnc_update_client

ui: remove 'sync' parameter from vnc_update_client

There is only one caller of vnc_update_client and that always passes false
for the 'sync' parameter.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20171218191228.31018-2-berrange@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 6af998db05aec9af95a06f84ad94f1b96785e667)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>