Adding support for dynamic membership with UDPU transport

Add a new object called totem.interface.dynamic to allow creation/deletion
of new child objects using the corosync-objctl utility:

to add new member:
linux# corosync-objctl -c totem.interface.dynamic.10-211-55-12

to delete an existing member:
linux# corosync-objctl -d totem.interface.dynamic.10-211-55-12

Corosync will dynamically add these members to the configuration and start
communicating with those nodes.

Signed-off-by: Anton Jouline <anton.jouline@cbsinteractive.com>
Reviewed-by: Steven Dake <sdake@redhat.com>