diagnostics.sh: fix background mode not getting any arguments

The shift of all option argument caused backgrounded instance to run as
if there no arguments were passed.

diagnostics.sh

@@ -129,20 +129,20 @@ while getopts "hlbBo:O:" opt; do
 	;;
 	esac
 done
-shift "$((OPTIND - 1))"
 
-if [ "$list_modules" = "y" ]; then
-	list_modules
+if [ "$background" = "y" -a "$TURRIS_DIAGNOSTICS_IN_BACKGROUND" != "1" ]; then
+	TURRIS_DIAGNOSTICS_IN_BACKGROUND=1 "$0" "$@" >/dev/null 2>&1 </dev/null &
 	exit 0
 fi
 
+shift "$((OPTIND - 1))"
 
-if [ "$background" = "y" -a "$TURRIS_DIAGNOSTICS_IN_BACKGROUND" != "1" ]; then
-	export TURRIS_DIAGNOSTICS_IN_BACKGROUND=1
-	"$0" "$@" >/dev/null 2>&1 </dev/null &
+if [ "$list_modules" = "y" ]; then
+	list_modules
 	exit 0
 fi
 
+
 # Clean the last output files
 if [ -n "$OUTPUT_FILE" ]; then
 	rm -rf "$OUTPUT_FILE"