Remove a bunch of unused CTS tests from continuous test build to save space.

BUG 2053298
diff --git a/tests/tests/media/Android.mk b/tests/tests/media/Android.mk
index d873ec0..2c4ade1 100644
--- a/tests/tests/media/Android.mk
+++ b/tests/tests/media/Android.mk
@@ -16,7 +16,7 @@
 
 include $(CLEAR_VARS)
 
-LOCAL_MODULE_TAGS := tests
+LOCAL_MODULE_TAGS := optional
 
 LOCAL_JAVA_LIBRARIES := android.test.runner