vnc: dont' try to connect if VM is unreachable
vnc: dont' try to connect if VM is unreachable

Add pre-flight checks to see if the VM is reachable before to
setup all the connections, and before to spawn remote-viewer.
Abort early if this is the case, without launching external binaries,
that could be orphaned later or leave stray popups.

davidvossel/kubevirt,kubevirt/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,rmohr/kubevirt,stu-gott/kubevirt,stu-gott/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt,kubevirt/kubevirt,davidvossel/kubevirt,rmohr/kubevirt,davidvossel/kubevirt,stu-gott/kubevirt