Fix passing Component to StreamManager

0a4acd12c3, which fixes #160, introduced
a regression as it assumed only Client may implement StreamClient, and
passing a component triggers an unconditional "client is not
disconnected" error.

stream_manager.go

@@ -114,10 +114,16 @@ func (sm *StreamManager) Stop() {
 
 func (sm *StreamManager) connect() error {
 	if sm.client != nil {
-		if c, ok := sm.client.(*Client); ok {
-			if c.CurrentState.getState() == StateDisconnected {
+		var scs *SyncConnState
+		if client, ok := sm.client.(*Client); ok {
+			scs = &client.CurrentState
+		}
+		if component, ok := sm.client.(*Component); ok {
+			scs = &component.CurrentState
+		}
+		if scs != nil && scs.getState() == StateDisconnected {
 			sm.Metrics = initMetrics()
-				err := c.Connect()
+			err := sm.client.Connect()
 			if err != nil {
 				return err
 			}
@@ -127,7 +133,6 @@ func (sm *StreamManager) connect() error {
 			return nil
 		}
 	}
-	}
 	return errors.New("client is not disconnected")
 }