Make AudioGroup.add locale safe

Explicitly use Locale.US in AudioGroup.add to avoid
unexpected results in some locales.

Change-Id: Ifb477ca590f630747e09e38ac2246d284b5c5bfc
diff --git a/java/android/net/rtp/AudioGroup.java b/java/android/net/rtp/AudioGroup.java
index 8c19062..8faeb88 100644
--- a/java/android/net/rtp/AudioGroup.java
+++ b/java/android/net/rtp/AudioGroup.java
@@ -19,6 +19,7 @@
 import android.media.AudioManager;
 
 import java.util.HashMap;
+import java.util.Locale;
 import java.util.Map;
 
 /**
@@ -146,7 +147,7 @@
         if (!mStreams.containsKey(stream)) {
             try {
                 AudioCodec codec = stream.getCodec();
-                String codecSpec = String.format("%d %s %s", codec.type,
+                String codecSpec = String.format(Locale.US, "%d %s %s", codec.type,
                         codec.rtpmap, codec.fmtp);
                 int id = nativeAdd(stream.getMode(), stream.getSocket(),
                         stream.getRemoteAddress().getHostAddress(),