Audio was the cause of the emulator becoming
unresponsive when not connected to an X11 session.
Disabling audio when no window is being rendered

Change-Id: I1f1736a87b07cc07c90ac170fa1e437b9df72f93
diff --git a/src/com/android/tradefed/targetprep/SdkAvdPreparer.java b/src/com/android/tradefed/targetprep/SdkAvdPreparer.java
index 423697f..e47984d 100644
--- a/src/com/android/tradefed/targetprep/SdkAvdPreparer.java
+++ b/src/com/android/tradefed/targetprep/SdkAvdPreparer.java
@@ -135,6 +135,7 @@
 
         if (!mWindow) {
             emulatorArgs.add("-no-window");
+            emulatorArgs.add("-no-audio");
         }
 
         if (mGpu) {