wait_for_vnc_port: allow to enforce IP family

wait_for_vnc_port: allow to enforce IP family

Most times a port was requested for a specified IP family (v4, v6)
only. Thus also ensure that the port from the respective family got
ready, else we may return on a false positive.

As we had no user setting the $timeout param we can add the $family
param as second one, it'll get used more often, so no need to put it
at the back.

As we do nothing if not defined this does not changes the behavior of
our users yet.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>