Allow installd to delete directories in staging dir

In order to support deleting session files after a staged session reaches
a final state, installd will need to delete the session directories from
/data/staging.

Bug: 123624108
Test: triggered 2 flows in which a staged session reaches a final state
and made sure installd can delete the session files

Change-Id: I76a7d4252d1e033791f67f268cf941672c5e6a3a
2 files changed