Correctly set audio mode

Fixes #4244
// FREEBIE

src/org/thoughtcrime/redphone/audio/CallAudioManager.java

@@ -1,8 +1,13 @@
 package org.thoughtcrime.redphone.audio;
 
+import android.content.Context;
+import android.media.AudioManager;
 import android.os.Build;
+import android.support.annotation.NonNull;
 import android.util.Log;
 
+import org.thoughtcrime.securesms.util.ServiceUtil;
+
 import java.io.FileDescriptor;
 import java.lang.reflect.Field;
 import java.net.DatagramSocket;
@@ -38,7 +43,13 @@ public class CallAudioManager {
     setMute(handle, enabled);
   }
 
-  public void start() throws AudioException {
+  public void start(@NonNull Context context) throws AudioException {
+    if (Build.VERSION.SDK_INT >= 11) {
+      ServiceUtil.getAudioManager(context).setMode(AudioManager.MODE_IN_COMMUNICATION);
+    } else {
+      ServiceUtil.getAudioManager(context).setMode(AudioManager.MODE_IN_CALL);
+    }
+
     try {
       start(handle);
     } catch (NativeAudioException | NoSuchMethodError e) {

src/org/thoughtcrime/redphone/call/InitiatingCallManager.java

@@ -127,6 +127,6 @@ public class InitiatingCallManager extends CallManager {
                                                  masterSecret.getResponderMacKey(),
                                                  masterSecret.getResponderSrtpSailt());
     this.callAudioManager.setMute(muteEnabled);
-    this.callAudioManager.start();
+    this.callAudioManager.start(context);
   }
 }

src/org/thoughtcrime/redphone/call/ResponderCallManager.java

@@ -157,7 +157,7 @@ public class ResponderCallManager extends CallManager {
                                                  masterSecret.getInitiatorMacKey(),
                                                  masterSecret.getInitiatorSrtpSalt());
     this.callAudioManager.setMute(muteEnabled);
-    this.callAudioManager.start();
+    this.callAudioManager.start(context);
   }
 
 }

src/org/thoughtcrime/securesms/util/ServiceUtil.java

@@ -3,6 +3,7 @@ package org.thoughtcrime.securesms.util;
 import android.app.Activity;
 import android.app.NotificationManager;
 import android.content.Context;
+import android.media.AudioManager;
 import android.net.ConnectivityManager;
 import android.telephony.TelephonyManager;
 import android.view.WindowManager;
@@ -28,4 +29,8 @@ public class ServiceUtil {
   public static TelephonyManager getTelephonyManager(Context context) {
     return (TelephonyManager)context.getSystemService(Context.TELEPHONY_SERVICE);
   }
+
+  public static AudioManager getAudioManager(Context context) {
+    return (AudioManager)context.getSystemService(Context.AUDIO_SERVICE);
+  }
 }