Check only if the app is installed on the other user for blob access.

There isn't a need to require that the app has permission on other
user as well. With this change, we are checking the apps existence
on other users to limit access such that apps won't be able to
access any more data than they would've accessed by having
INTERACT_ACROSS_USERS permission and talking to their instances
on other users.

Bug: 175844032
Test: atest --test-mapping apex/blobstore
Change-Id: I6f13e3e7a240d55c02aecf31e10f750b9e4d5702