mxqd: Remove superfluous "unknown pid returned" warning

Currently mxqd emits a warning if a child process, which is not
associated to a pid of a running job, finishes.

With the previous changes, when a job is killed by SIGKILL, we correctly
avoid to kill the reaper process so that the job is finished normally
via fspool. Because of that change it now happens more often that a job
is already done for mxqd when the reaper process terminates normally a
little later. So the condition that we see a terminating child, which is
not related to a running job, is expected behaviour. Remove the warning.

Previously we had "reaper died" messages in the logfile when mxqd sent a
KILL signal to a job, because it  killed the reaper with it.

mxqd.c

@@ -2412,13 +2412,6 @@ int catchall(struct mxq_server *server)
 
         jlist = server_get_job_list_by_pid(server, siginfo.si_pid);
         if (!jlist) {
-            mx_log_warning("unknown pid returned.. si_pid=%d si_uid=%d si_code=%d si_status=%d getpgid(si_pid)=%d getsid(si_pid)=%d",
-                            siginfo.si_pid,
-                            siginfo.si_uid,
-                            siginfo.si_code,
-                            siginfo.si_status,
-                            getpgid(siginfo.si_pid),
-                            getsid(siginfo.si_pid));
             /* collect child, ignore status */
             pid = waitpid(siginfo.si_pid, NULL, WNOHANG);
             if (pid != siginfo.si_pid)