Fix minor leak in localauth RULE handling

In aname_replacer(), initialize current, null it when transferring
ownership to the caller, and free it on cleanup.  Otherwise it leaks
on failure.  Reported by Bean Zhang.

https://github.com/krb5/krb5/commit/dbc2ccd6d9ff546e2f4af54898c952ffa4eebf44
Author: Greg Hudson <ghudson@mit.edu>
Commit: dbc2ccd6d9ff546e2f4af54898c952ffa4eebf44
Branch: master
 src/lib/krb5/os/localauth_rule.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)