Revoke/Grant permission for current user

ScopedStorageHostTest & ScopedStorageCoreHostTest revokes/grants storage
permissions for device test. Previously, in the revokePermission() &
grantPermission() method we always revoked or granted permission for
USER_SYSTEM. But while running as secondary_user we should revoke/grant
permission for secondary_user.

Changed revokePermission() and grantPermission() to revoke and grant
permission for current user.

Also changed testAccess_Directory to use TradefedContentProvider to
create/delete directory instead of shell command.

Test: atest ScopedStorageHostTest on secondary user
Test: atest ScopedStorageCoreHostTest on secondary user

Bug: 172977876
Bug: 182389935

(cherry picked from commit I3469c75c5f0a17e511424457d0ac699bb519de56)
(cherry picked from commit 71541f21da04b22eefa2f4ab06a4a3afaff74c65)
Merged-In: I3469c75c5f0a17e511424457d0ac699bb519de56
Change-Id: I3469c75c5f0a17e511424457d0ac699bb519de56