totemconfig: Explicitly pass IP version

If resolver was set to prefer IPv6 (almost always) and interface section
was not defined (almost all config files created by pcs), IP version was
set to mcast_addr.family. Because mcast_addr.family was unset (reset to
zero), IPv6 address was returned causing failure in totemsrp.
Solution is to pass correct IP version stored in
totem_config->ip_version.

Patch also simplifies get_cluster_mcast_addr. It was using mix of
explicitly passed IP version and bindnet IP version.

Also return value of get_cluster_mcast_addr is now properly checked.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>