Ensure the HostsideVpnTests passes with keyguard locked.

The test app used in CtsHostsideNetworkTests already dismisses
the keyguard for its own activity, but that doesn't work for the
VPN tests. This is because as soon as the VPN dialog appears, the
test activity is no longer in the foreground and the keyguard
comes back. As a result, the test cannot click on the VPN dialog.

Test: test-only change
Change-Id: I7be1d7fb46a2f9547bc5325d75b5bd5546e6dc18

tests/cts/hostside/app/src/com/android/cts/net/hostside/MyActivity.java

@@ -17,6 +17,7 @@
 package com.android.cts.net.hostside;
 
 import android.app.Activity;
+import android.app.KeyguardManager;
 import android.content.Intent;
 import android.os.Bundle;
 import android.view.WindowManager;
@@ -34,6 +35,11 @@ public class MyActivity extends Activity {
         getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON
                 | WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
                 | WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
+
+        // Dismiss the keyguard so that the tests can click on the VPN confirmation dialog.
+        // FLAG_DISMISS_KEYGUARD is not sufficient to do this because as soon as the dialog appears,
+        // this activity goes into the background and the keyguard reappears.
+        getSystemService(KeyguardManager.class).requestDismissKeyguard(this, null /* callback */);
     }
 
     @Override