sepolicy: Adjust policy for migrate_legacy_obb_data.sh

Required to check if migration is necessary and migrate obb contents

Bug: 136199978
Test: make
Change-Id: I23890e4eeea1da7791e25ce5c9584b1abe94f440
(cherry picked from commit 793dc8f8da2bbcb954670bfbd53a0038328e8473)
2 files changed