Fix : Exception name for ProtocolError.

Thanks ricard33!
Fix : reset self.nb_check_received before the main loop in scheduler.py

The stats were incorrect in debug when restarting the arbiter.
Multisite version update

Update MKVER variable to Multisite lastest stable version (MKVER="1.2.2p2")
Merge pull request #909 from Denetariko/patch-5

Multisite version update