totemconfig: Check for duplicate nodeids

Having duplicate nodeids in corosync.conf can play havoc with a cluster,
so (as suggested by someone on this list) here is some code to check
that all nodeids are unique. Even if a nodeid is not specified it will
check to be sure that the ID generated from the IP address (ipv4 only)
does not clash with one that is provided.

It logs all non-unique nodeids to syslog, but only the last is reported
on the command-line to the user which should be enough to get them to
check further. At startup this will cause corosync to fail to start.

Signed-off-by: Christine Caulfield <ccaulfie@redhat.com>