In the normal course of execution, md5.contents allocated by
kg_checksum_channel_bindings() in make_ap_req_v1() is freed in
make_gss_checksum(). But when there is a failure in
krb5_mk_req_extended() or in make_gss_checksum() before free is
called, the memory leaks.
This patch frees the memory unconditionally in make_ap_req_v1().