Added library to dump the mcast messages from other LVS in the same network

To be used by lvsm to manually synchronize LVS in a symmetric cluster.

To launch in debug mode:
=> LVSSYNCNR set to anything if name resolution is desired (no fqdn support)
=> LVSSYNCINT specify which interface to listen the mcast packets. Leavy empty for default
LVSSYNCNR=1 LVSSYNCINT=eth0 python lvssync.py