krb5: Fix error condition

‘ret’ can only ever be equal to zero.

Found by Coverity (Samba CID 1518754).

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>

lib/krb5/store.c

@@ -968,7 +968,7 @@ krb5_ret_data(krb5_storage *sp,
 	bytes = sp->fetch(sp, data->data, size);
 	if (bytes < 0 || bytes != size) {
             krb5_data_free(data);
-	    return (ret < 0)? errno : sp->eof_code;
+	    return (bytes < 0)? errno : sp->eof_code;
 	}
     }
     return 0;