tmpdir-setup: Don't cleanup asynchronously

When mxqd restarts and finds finished jobs, it calls the tmpdir cleanup
code for these jobs.

As part of the recovery procedure, it later scans the system for any
leftover mounts. When the regular tmpdir cleanup is done asynchronously,
mxqd might discover a directory which is in the progress of being
dismounted but still exists in which case it calls the tmpdir
cleanup code a second time.

There is no harm done, the jobs completed normally. The second
attempted cleanup just produces some error messages in the logfile

This bug is only triggered when jobs complete while mxqd is stopped.

As the "old style" tmpdir setup is going away anyway, don't invent
something complicated here and just do the cleanup synchronously.

helper/tmpdir-setup

@@ -52,12 +52,10 @@ cmd_cleanup() {
     (( $# == 1 )) || usage
     MXQ_JOBID=$1
 
-    (
-        shopt -s dotglob;
-        rm -rf /dev/shm/mxqd/mnt/job/$MXQ_JOBID/*
-        umount /dev/shm/mxqd/mnt/job/$MXQ_JOBID
-        rmdir /dev/shm/mxqd/mnt/job/$MXQ_JOBID
-    ) &
+    shopt -s dotglob;
+    rm -rf /dev/shm/mxqd/mnt/job/$MXQ_JOBID/*
+    umount /dev/shm/mxqd/mnt/job/$MXQ_JOBID
+    rmdir /dev/shm/mxqd/mnt/job/$MXQ_JOBID
 }
 
 (( $# > 0 )) || usage