Fix leak in FAST OTP client processing

In set_pa_data(), after encoding the OTP request and stealing the
pointer from the resulting krb5_data object, free the krb5_data
container.

(cherry picked from commit 7029efc)

ticket: 8443
version_fixed: 1.13.7

src/lib/krb5/krb/preauth_otp.c

@@ -830,6 +830,7 @@ set_pa_data(const krb5_pa_otp_req *req, krb5_pa_data ***pa_data_out)
         goto error;
     out[0]->contents = (krb5_octet *)tmp->data;
     out[0]->length = tmp->length;
+    free(tmp);
 
     *pa_data_out = out;
     return 0;