[jingle] Mimic Manager.connection() in JingleTransportManager

Eventually JingleTransportManager should be a subclass of Manager (or
be replaced by Manager), as JingleTransportManager holds a strong
reference to the XMPPConnection. This could cause memory leaks. But
for now, we mimic the Manager API in JingleTransportManger to make a
future transition to Manager easier.

smack-extensions/src/main/java/org/jivesoftware/smackx/jingle/transports/JingleTransportManager.java

@@ -36,6 +36,10 @@ public abstract class JingleTransportManager<D extends JingleContentTransport> i
     }
 
     public XMPPConnection getConnection() {
+        return connection();
+    }
+
+    public XMPPConnection connection() {
         return connection;
     }