Override apexes with LOCAL_OVERRIDES_MODULES

APEXes are ETC type, which should be overridden via
LOCAL_OVERRIDES_MODULES. This change fixes a bug that
LOCAL_OVERRIDES_PACKAGES was used for APEXes.

Bug: 140792287
Test: m
Test: add com.google.android.tzdata to PRODUCT_PACKAGES and build.
/system/apex/com.google.android.tzdata.apex exists, but
/system/apex/com.android.tzdata.apex doesn't.

Change-Id: Id65743b36e0b706d6ffd8cae0597cc0a42a83fb7