Fix memory leak in SPAKE kdcpreauth module

Commit ff57dc682a27bd205d715f3c0bed84890f2453c4 introduced a memory
leak into verify_response().  reply_key is no longer passed to the
callback and therefore needs to be freed by this function.

[ghudson@mit.edu: rewrote commit message]

(cherry picked from commit 445e1b32767af3041ffd1823996d05ffec6fc9d5)

https://github.com/krb5/krb5/commit/a7a99db31c532c5616814853354a048fc865df06
Author: sashan <anedvedicky@gmail.com>
Committer: Greg Hudson <ghudson@mit.edu>
Commit: a7a99db31c532c5616814853354a048fc865df06
Branch: krb5-1.20
 src/plugins/preauth/spake/spake_kdc.c | 1 +
 1 file changed, 1 insertion(+)