Kobo: Don't exit the startup script on shutdown when started via KSM.

This ensures we keep displaying our own stuff, without KSM interference.

Fix #9748

platform/kobo/koreader.sh

@@ -611,10 +611,20 @@ if [ ${RETURN_VALUE} -ne ${KO_RC_HALT} ]; then
         # if we were called from advboot then we must reboot to go to the menu
         # NOTE: This is actually achieved by checking if KSM or a KSM-related script is running:
         #       This might lead to false-positives if you use neither KSM nor advboot to launch KOReader *without nickel running*.
-        if ! pgrep -f kbmenu >/dev/null 2>&1; then
+        if ! pkill -0 kbmenu; then
             /sbin/reboot
         fi
     fi
+else
+    if [ "${VIA_NICKEL}" = "false" ]; then
+        if pkill -0 kbmenu; then
+            # If we were started by KSM and requested an exit, attempt to *NOT* exit the script,
+            # so as not to re-enter KSM at all, to make sure the device powers off with our own ScreenSaver displayed.
+            # NOTE: This might not be fool-proof, as a poweroff might take longer than that,
+            #       or we might be interrupted early by signals.
+            sleep 10
+        fi
+    fi
 fi
 
 # Wipe the clones on exit