trigger the update channel for slave -> slave transitions

Fixes a bug where master changes that did not involve the
local node were not triggering updates.

masterelection/masterelection.go

@@ -63,16 +63,15 @@ func (m *MasterElection) GetMasterAddr() string {
 }
 
 func (m *MasterElection) setState(state int) {
-	if m.State == state {
-		return
-	}
 	log.Printf("masterelection: %s -> %s",
 		stateToString(m.State),
 		stateToString(state))
+	// Order is important here: set state before triggering the
+	// update channel so that the receiver sees the right value.
+	m.State = state
 	if m.StateChange != nil {
 		m.StateChange <- state
 	}
-	m.State = state
 }
 
 func (m *MasterElection) stopper() {