Added android.test.mock to PRODUCT_PACKAGES

Adds android.test.mock.jar to the /system/framework
directory. That will allow it to be dynamically included
with a uses-library manifest entry.

Bug: 30188076
Test: flash and check contents of /system/framework
Change-Id: I3ea0e558276176edd21e24c8337980c5c02a652e
diff --git a/target/product/base.mk b/target/product/base.mk
index a671203..89027bf 100644
--- a/target/product/base.mk
+++ b/target/product/base.mk
@@ -23,6 +23,7 @@
     appops \
     am \
     android.policy \
+    android.test.mock \
     android.test.runner \
     app_process \
     applypatch \