Fix issue 2378022: AudioService should direct volume control to STREAM_VOICE_CALL stream when STREAM_VOICE_CALL stream is active.

Modified AudioService.getActiveStreamType() so that STREAM_VOICE_CALL is selected when a track using this stream
type is playing.

Chanded isMusicActive() for a more generic isStreamActive(stream) method in AudioSystem, IAudioFlinger and AudioFlinger.
diff --git a/libs/audioflinger/AudioFlinger.h b/libs/audioflinger/AudioFlinger.h
index 12c90eb..52999b1 100644
--- a/libs/audioflinger/AudioFlinger.h
+++ b/libs/audioflinger/AudioFlinger.h
@@ -100,7 +100,7 @@
     virtual     status_t    setMicMute(bool state);
     virtual     bool        getMicMute() const;
 
-    virtual     bool        isMusicActive() const;
+    virtual     bool        isStreamActive(int stream) const;
 
     virtual     status_t    setParameters(int ioHandle, const String8& keyValuePairs);
     virtual     String8     getParameters(int ioHandle, const String8& keys);
@@ -506,7 +506,7 @@
         virtual     float       streamVolume(int stream) const;
         virtual     bool        streamMute(int stream) const;
 
-                    bool        isMusicActive() const;
+                    bool        isStreamActive(int stream) const;
 
                     sp<Track>   createTrack_l(
                                     const sp<AudioFlinger::Client>& client,