Prevent apk-in-apex from being registered under wrong apex

Without this fix, an apk-in-apex located in path
/apex/com.android.mediaprovider will be added as apk-in-apex
for com.android.media too, just because they have the same
prefix.

Added a info log too to make it easier to understand which apk-in-apex
is being registered under which apex.

Bug: 170640411
Test: Manual testing
Change-Id: Idc989ac84777589b4bdd72012833cdbdab7e872c