Fix loophole in module expansion.

Previously we only expanded product_MODULES with LOCAL_REQUIRED_MODULES,
but not modules introduced by LOCAL_SHARED_LIBRARIES; Later we did a further
shared libary expansion in vendor_module_check.mk.
It couldn't track C in the following case:
A : B, by LOCAL_SHARED_LIBRARIES; B : C, by LOCAL_REQUIRED_MODULES.

With this change, we transformed the LOCAL_SHARED_LIBRARIES dependencies
into LOCAL_REQUIRED_MODULES dependencies before doing the required
module expansion and the loophole is closed.
All module names are now expanded to product_MODULES now and it makes
vendor_module_check.mk simpler.

Change-Id: I8835a478d2ce0ce10601a8449f446f07b01c2b7f