Fix wrong LEGACY_STORAGE appop grant

Apps with WRITE_MEDIA_STORAGE permission should only be granted the
LEGACY_STORAGE appop while they target <R. This was the original
intention, but Ic24372348118ad9ed818a28f377e0decc78b9ecc changed
the behavior to allow the legacy appop for apps with
WRITE_MEDIA_STORAGE permission regardless of target SDK.

This change prevents granting the legacy storage appop to
apps with WRITE_MEDIA_STORAGE permission if they target
>=R. Additionally, we also deny the appop if they target >=R.

Bug: 190001005
Test: atest RestrictedStoragePermissionTest
Test: atest PreserveLegacyStorageHostTest
Test: Manually installed a targetR app with WRITE_MEDIA_STORAGE
permission and verified that legacy_storage was ignored
Change-Id: Icd804e289491a2416bcb9b5f78012314027af047