Spice port registration is delayed until the server is started. But
ports created after are not being registered. If the server is already
started, do vmc_register_interface() to register it from
qemu_chr_open_spice_port().

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Tested-by: Victor Toso <victortoso@redhat.com>
Message-id: 20190221110703.5775-8-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>