change how instant app installer is updated

. only pay attention to package changes if there's no
  installer or the changed package is the installer
. always update the installer component, even if the
  resolved component is identical [the install paths
  might have updated]

Change-Id: I16eba07ccdb55f5cb61ba6172e71ce1698445fa5
Fixes: 36740490
Test: Manually install/remove/update the installer and see that the component is updated