Fix regression in RCC.editMetadata(false)

Found a very simple fix. Just set the cached metadata so we have
it to copy over when editMetadata(false) is called.

bug:17796693
Change-Id: Ib27f0c3d28e7f2a3c7d9495697f36c8045e2bcf6

media/java/android/media/RemoteControlClient.java

@@ -572,7 +572,8 @@ import java.lang.IllegalArgumentException;
 
                 // USE_SESSIONS
                 if (mSession != null && mMetadataBuilder != null) {
-                    mSession.setMetadata(mMetadataBuilder.build());
+                    mMediaMetadata = mMetadataBuilder.build();
+                    mSession.setMetadata(mMediaMetadata);
                 }
                 mApplied = true;
             }