Yixiong Zou reported a problem where on some OSes the aisexec
couldn't join the multicast group. This problem fixed. Also
changed binding rules for sockets relating to the group messaging.
see detailed changlogs for more details.

BKrev: 40d9efacQooUDhv3APjn55QVVjMueg


git-svn-id: http://svn.fedorahosted.org/svn/corosync/trunk@27 fd59a12c-fef9-0310-b244-a6a79926bd2f