mxqd: Remove RLIMIT_CPU usage for runtime limitation

The current code applies a RLIMIT_CPU limit to jobs with `job_threads == i`.
This is incorrect, as such jobs can still get more processors if they
require more server slots because of their memory demands.

Since mxqd can now monitor and reliably kill jobs that exceed their
allowed runtime, this code is obsolete and no longer useful.

There is no reason to fix this code, so remove it entirely.

mxqd.c

@@ -1018,17 +1018,6 @@ static void exec_reaper(struct mxq_server *server,struct mxq_group_list *glist,
         mx_log_err("job=%s(%d):%lu:%lu setrlimit(RLIMIT_CORE, ...) failed: %m",
                     group->user_name, group->user_uid, group->group_id, job->job_id);
 
-    /* set single threaded time limits */
-    if (group->job_threads == 1) {
-            /* set cpu time limits - hardlimit is 105% of softlimit */
-            rlim.rlim_cur = group->job_time*60;
-            rlim.rlim_cur = group->job_time*63;
-
-            if (setrlimit(RLIMIT_CPU, &rlim)  == -1)
-                mx_log_err("job=%s(%d):%lu:%lu setrlimit(RLIMIT_CPU, ...) failed: %m",
-                            group->user_name, group->user_uid, group->group_id, job->job_id);
-    }
-
     if (initgroups(passwd->pw_name, group->user_gid) == -1) {
         mx_log_err("job=%s(%d):%lu:%lu initgroups() failed: %m",
             group->user_name, group->user_uid, group->group_id, job->job_id);