Update monitor_nchan

sbin/monitor_nchan

@@ -19,7 +19,9 @@ nchan_stop() {
 nchan_start() {
   [[ -e $nchan_list ]] || return
   while IFS=$'\n' read -r nchan; do
-    $nchan &>/dev/null &
+    if ! pgrep -f $nchan >/dev/null; then
+      $nchan &>/dev/null &
+    fi
   done < $nchan_list
   rm -f $nchan_list
 }