multi: make sure missionControlStore catches done signal

This commit makes sure `missionControlStore` catches the shutdown signal
when draining the ticker. A few debug logs are added to aid the process.

discovery/gossiper.go

@@ -750,8 +750,8 @@ func (d *AuthenticatedGossiper) Stop() error {
 }
 
 func (d *AuthenticatedGossiper) stop() {
-	log.Info("Authenticated Gossiper is stopping")
-	defer log.Info("Authenticated Gossiper stopped")
+	log.Debug("Authenticated Gossiper is stopping")
+	defer log.Debug("Authenticated Gossiper stopped")
 
 	d.blockEpochs.Cancel()