Change setPrimaryStorageUuid to handle it for the current user

- It used hard coded user 0 and that breaks it for
  secondary users. Current user should be enough if this move is
  triggered from settings which is run from the current user.

- For device with no user switching from user 0, this should
  not make any differences.

- This change also fixes failure of CTS
  android.appsecurity.cts.AdoptableHostTest#testPrimaryStorage.

- In longer term, we need separate setPrimaryStorageUuidAsUser API
  to control it per each user.

Bug: 174593750
Test: atest android.appsecurity.cts.AdoptableHostTest#testPrimaryStorage
Change-Id: I87c821903987d22e8d26ade92120b99a33897168