Prevent weird messages from rpc lib on start (Fixes #3209): (#3212)

This is done by not making the methods of the BucketMetaState interface
as methods (via type nesting) on the type implementing
RPCs (s3PeerAPIHandlers).

cmd/s3-peer-router.go

@@ -27,7 +27,7 @@ const (
 )
 
 type s3PeerAPIHandlers struct {
-	*localBMS
+	bms BucketMetaState
 }
 
 func registerS3PeerRPCRouter(mux *router.Router) error {

cmd/s3-peer-rpc-handlers.go

@@ -54,7 +54,7 @@ func (s3 *s3PeerAPIHandlers) SetBucketNotificationPeer(args *SetBNPArgs, reply *
 		return errInvalidToken
 	}
 
-	return s3.UpdateBucketNotification(args)
+	return s3.bms.UpdateBucketNotification(args)
 }
 
 // SetBLPArgs - Arguments collection to SetBucketListenerPeer RPC call
@@ -74,7 +74,7 @@ func (s3 *s3PeerAPIHandlers) SetBucketListenerPeer(args *SetBLPArgs, reply *Gene
 		return errInvalidToken
 	}
 
-	return s3.UpdateBucketListener(args)
+	return s3.bms.UpdateBucketListener(args)
 }
 
 // EventArgs - Arguments collection for Event RPC call
@@ -96,7 +96,7 @@ func (s3 *s3PeerAPIHandlers) Event(args *EventArgs, reply *GenericReply) error {
 		return errInvalidToken
 	}
 
-	return s3.SendEvent(args)
+	return s3.bms.SendEvent(args)
 }
 
 // SetBPPArgs - Arguments collection for SetBucketPolicyPeer RPC call
@@ -117,5 +117,5 @@ func (s3 *s3PeerAPIHandlers) SetBucketPolicyPeer(args *SetBPPArgs, reply *Generi
 		return errInvalidToken
 	}
 
-	return s3.UpdateBucketPolicy(args)
+	return s3.bms.UpdateBucketPolicy(args)
 }