Only run xcompmgr if openbox is running

debian/changelog

@@ -1,3 +1,9 @@
+raspi-config (20210604) bullseye; urgency=medium
+
+  * Disable xcompmgr when openbox not running
+
+ -- Simon Long <simon@raspberrypi.com>  Fri, 04 Jun 2021 13:53:42 +0100
+
 raspi-config (20210212) buster; urgency=medium
 
   * Update boot order menu

debian/compat

@@ -1 +1 @@
-9
+10

usr/lib/raspi-config/cmstart.sh

@@ -1,4 +1,6 @@
 #!/bin/sh
 if grep -q okay /proc/device-tree/soc/v3d@7ec00000/status 2> /dev/null || grep -q okay /proc/device-tree/soc/firmwarekms@7e600000/status 2> /dev/null ; then
-    exec xcompmgr -aR
+    if ps ax | grep -v grep | grep -q openbox ; then
+        exec xcompmgr -aR
+    fi
 fi