(manual) backport of 1.7's master_state changes
Merge pull request #254 from Incubaid/master_state_1.6

(manual) backport of 1.7's master_state changes
Merge remote-tracking branch 'origin/1.6' into ARAKOON-442-1.6

* origin/1.6:
  (manual) backport of 1.7's master_state changes

Conflicts:
	src/paxos/multi_paxos_fsm.ml