totemconfig: refactor nodelist_to_interface func

Move finding of bindaddr in nodelist to generally usable function
totem_config_find_local_addr_in_nodelist and refactor
config_convert_nodelist_to_interface function to use it.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>