mxqd: Do not disconnect from mysql server on job start

We no longer need to disconnect from the mysql server and reconnect to
it every time we start a job now that er exec() the reaper. The socket
ist set to CLOEXEC, so it isn't leaked and the memory image of the mysql
library is replaced anyway.

mxqd.c

@@ -1202,8 +1202,6 @@ static unsigned long start_job(struct mxq_group_list *glist)
     mx_free_null(job->host_cpu_set_str);
     job->host_cpu_set_str = mx_cpuset_to_str(&job->host_cpu_set);
 
-    mx_mysql_disconnect(server->mysql);
-
     pid = fork();
     if (pid < 0) {
         mx_log_err("fork: %m");
@@ -1219,8 +1217,6 @@ static unsigned long start_job(struct mxq_group_list *glist)
 
     gettimeofday(&job->stats_starttime, NULL);
 
-    mx_mysql_connect_forever(&(server->mysql));
-
     job->host_pid   = pid;
     job->host_slots = glist->slots_per_job;
     res = mxq_set_job_status_running(server->mysql, job);