Make TestCallActivity Theme.NoDisplay

This prevents the activity from bringing up the UI at all,
which makes the initiation of a test call more realistic from the
ActivityManager's perspective since calls are usually
generated from the background.

Change-Id: Ie8893d38593f61689b8e2cdfd2e17d5efef3d79e
diff --git a/testapps/AndroidManifest.xml b/testapps/AndroidManifest.xml
index c8d7105..3483391 100644
--- a/testapps/AndroidManifest.xml
+++ b/testapps/AndroidManifest.xml
@@ -54,6 +54,7 @@
         </service>
 
         <activity android:name="com.android.server.telecom.testapps.TestCallActivity"
+                  android:theme="@android:style/Theme.NoDisplay"
                   android:label="@string/testCallActivityLabel"
                   android:process="com.android.server.telecom.testapps.TestInCallService">
             <intent-filter>