Add flags to restorecon_recursive to traverse filesystems

Use to solve the problem of tracefs conditionally being mounted
under debugfs and needing restorecon'd without boot performance
penalty.

Also move skip-ce to a flag for consistency.

Test: Check that trace_mount has correct attributes after boot
Bug: 32849675
Change-Id: Ib6731f502b6afc393ea5ada96fa95b339f14da49