Emit unconditional module load only when inherit/include is on the top level.

That is, when a makefile contains
```
ifneq (,$(foo))
  $(call inherit-product,module.mk)
endif
```

module.mk has to be present only if `foo` is set.

Fixes: 200163602
Test: internal
Change-Id: Ic5f10ce8d49d6b87162bfe77922bba5e2cce228b