Fixups for read-only store tests
Fixups for read-only store tests

* After we're done initializing a read-only store for a test, shut it
  down so that we'll be able to delete it when cleaning up later.
* When mounting a layer that inherits from read-only layers, don't
  forget to pass the read-only store's location to the CLI helper.

Signed-off-by: Nalin Dahyabhai <f562fcb2a0b898bf0be1afc867ea92325d8f825f@redhat.com>

containers/storage,rhatdan/storage,rhatdan/storage,containers/storage,rhatdan/storage,containers/storage