Change framework services tests' runner

Change the test runner to android.support.test.runner.AndroidJUnitRunner
This newer runner support Mockito tests. See b/8138651
This should at least fix RankingHelperTest here.

Change-Id: I68e4f33939478e1ea59a3860d5ded1cd22a47989
diff --git a/services/tests/servicestests/Android.mk b/services/tests/servicestests/Android.mk
index 33979b1..3ad26d3 100644
--- a/services/tests/servicestests/Android.mk
+++ b/services/tests/servicestests/Android.mk
@@ -13,6 +13,7 @@
     services.net \
     easymocklib \
     guava \
+    android-support-test \
     mockito-target
 
 LOCAL_JAVA_LIBRARIES := android.test.runner