server: make sure we clear vdagent and update mouse mode on agent disconnect
server: make sure we clear vdagent and update mouse mode on agent disconnect

The check this patch removes causes us to not set vdagent to NULL, nor
update the mouse mode when the guest agent disconnects when no client is
attached. Which leads to a non working mouse, and on agent reconnect a
"spice_server_char_device_add_interface: vdagent already attached" message
instead of a successful re-add of the agent interface .

fgouget/spice,mathslinux/spice,elmarco/spice,alon/spice-server,mathslinux/spice,freedesktop-unofficial-mirror/spice__spice,freedesktop-unofficial-mirror/spice__spice,elmarco/spice,mathslinux/spice,SPICE/spice,elmarco/spice,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,fgouget/spice,dezelin/spice,dezelin/spice,fgouget/spice,alon/spice-server,mathslinux/spice,alon/spice-server,elmarco/spice,dezelin/spice,SPICE/spice,dezelin/spice,freedesktop-unofficial-mirror/spice__spice,ya-mouse/spice,Fantu/spice,Fantu/spice,ya-mouse/spice,freedesktop-unofficial-mirror/spice__spice,alon/spice-server,alon/spice-server,Fantu/spice,mathslinux/spice,Fantu/spice,dezelin/spice,elmarco/spice,fgouget/spice,ya-mouse/spice