KVM: enable VNC if a VNC_BIND_ADDRESS is defined
KVM: enable VNC if a VNC_BIND_ADDRESS is defined

We'll also enable a tablet usb device, as suggested by the kvm man page.

Reviewed-by: iustinp


apyrgio/snf-ganeti,mbakke/ganeti,dimara/ganeti,grnet/snf-ganeti,ganeti-github-testing/ganeti-test-1,andir/ganeti,apyrgio/ganeti,yiannist/ganeti,yiannist/ganeti,mbakke/ganeti,yiannist/ganeti,ganeti/ganeti,apyrgio/snf-ganeti,grnet/snf-ganeti,dimara/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti,leshchevds/ganeti,apyrgio/ganeti,leshchevds/ganeti,ganeti/ganeti,mbakke/ganeti,onponomarev/ganeti,andir/ganeti,leshchevds/ganeti,onponomarev/ganeti,bitemyapp/ganeti,andir/ganeti,bitemyapp/ganeti