These have been obsoleted since they were first written (in commit
"cred: add proc_set_cred helper", daf63fd2f9a8d040, r280130) by some
subsequent commits ("proc: refactor clearing credentials into
proc_unset_cred", 5a90435ccfed8e1e, r361448 ; "cred: distribute
reference count per thread", 1724c563e62fa800, r361993).
No functional change.