Remove mount hack

Now that fuse is default, this hack can be removed

BUG: 147137425
Test: manual, R targeting app with requestLegacyExternalStorage can
access file paths.
Test: atest CtsDeqpTestCases
Test: atest RestrictedPermissionsTest
Test: atest RestrictedStoragePermissionSharedUidTest

Change-Id: Iafa69be2624427d41b844c943d41d0b72707a1e7