cman members are queried in response to a callback,
and members sometimes leave and rejoin between queries
(e.g. when they leave and rejoin before corosync
detects they left.)
This means that simply checking if a node is a member
in consecutive queries sometimes misses events. We
need to compare the incarnation numbers of members
from consecutive queries to avoid this.
I was confused initially by the static ringid seq since its contents are
only used in the statechange() function, but it's consistent with other
variables and is useful for debugging, so ACK.