Fix directory where CtsTestStubs.apk is found.

Empirically, it's now found in a subdirectory named CtsTestStubs.

Change-Id: Iae50c37ac7655f0b32cc2cc5a1b50371d1397b54
diff --git a/testrunner/runtest.py b/testrunner/runtest.py
index d367904..f9f4771 100755
--- a/testrunner/runtest.py
+++ b/testrunner/runtest.py
@@ -376,7 +376,7 @@
         if is_cts:
           # hack! hardcode install of CtsTestStubs
           out = android_build.GetTestAppPath()
-          abs_install_path = os.path.join(out, "CtsTestStubs.apk")
+          abs_install_path = os.path.join(out, "CtsTestStubs", "CtsTestStubs.apk")
           logger.Log("adb install -r %s" % abs_install_path)
           logger.Log(self._adb.Install(abs_install_path))