ui: rename vnc_init_state to vnc_start_protocol

Rename the vnc_init_state method to reflect what its actual
purpose is, to discourage future devs from using it for more
general state initialization.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-id: 1475163940-26094-10-git-send-email-berrange@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>