jack: initialize jd->client after !jd check

Prepare the next patch: make the "!jd" check independent of the
jd->client initialization.  This way we can change the "jd"
initialization semantics later.

src/audioOutputs/audioOutput_jack.c

@@ -337,13 +337,13 @@ static int jack_openDevice(AudioOutput *audioOutput)
 		DEBUG("connect!\n");
 		jd = newJackData();
 		audioOutput->data = jd;
+	}
 
-		if (connect_jack(audioOutput) < 0) {
+	if (jd->client == NULL && connect_jack(audioOutput) < 0) {
 		freeJackData(audioOutput);
 		audioOutput->open = 0;
 		return -1;
 	}
-	}
 
 	set_audioformat(audioOutput);
 	audioOutput->open = 1;