Call hook in java_sdk_library after droidstubs generation

Currently, droidstubs module create java_api_contribution module, but
when a java_sdk_library module dynamically creates a droidstubs module,
java_api_contribution is not created as the hook inside droidstubs get
lost. Therefore, call hook inside sdk_library after creating the
droidstubs module.

Test: m
Change-Id: I68bf1d796f6f9a6f81011ae35e4991b6ed1421ea