mxqd: Do not disconnect from mysql before helper call

The helpers are trusted code, they won't do something nasty with the
connected mysql socket. So don't disconnect from and reconnect to the
mysql server when we call the tmpdir-setup helper.

mxqd.c

@@ -1308,7 +1308,6 @@ static unsigned long start_job(struct mxq_group_list *glist)
     }
 
     if (group->job_tmpdir_size > 0) {
-        mx_mysql_disconnect(server->mysql);
         char *argv[] = {
             tmpdir_script,
             "create",
@@ -1321,7 +1320,6 @@ static unsigned long start_job(struct mxq_group_list *glist)
         free(argv[2]);
         free(argv[3]);
         free(argv[4]);
-        mx_mysql_connect_forever(&(server->mysql));
         if (status == -1) {
             mx_log_err("create job tmpdir: %m");
             mxq_unload_job_from_server(server->mysql, job->job_id);