QmlProfiler: Don't let timer run if we cannot connect to port

Previously the timer was started as soon as we connect, but we
should actually make sure the service is there.

Change-Id: Ic59ccb4a402a54dc1fc1f0c92ca2f80dad436581
Reviewed-by: Christiaan Janssen <christiaan.janssen@nokia.com>

src/libs/qmljsdebugclient/qmlprofilertraceclient.cpp

@@ -88,6 +88,11 @@ void QmlProfilerTraceClient::clearData()
     emit cleared();
 }
 
+bool QmlProfilerTraceClient::isEnabled() const
+{
+    return status() == Enabled;
+}
+
 bool QmlProfilerTraceClient::isRecording() const
 {
     return d->recording;