[init.d] Ensure control file is removed

Ensure /tmp/openwisp/applying_conf is removed to avoid
unpredictable behaviour.

openwisp-config/files/openwisp.init

@@ -77,15 +77,18 @@ reload_service() {
 	logger -s "$PROG_NAME received reload trigger" \
 		   -t openwisp \
 		   -p daemon.info
+	local control_file=/tmp/openwisp/applying_conf
 	# avoid reloading while configuration is being applied
 	# will wait for a maximum of 30 seconds
 	for i in $(seq 1 30); do
-		if [ -f "/tmp/openwisp/applying_conf" ]; then
+		if [ -f $control_file ]; then
 			sleep 1
 		else
 			break
 		fi
 	done
+	# ensure control file is removed
+	rm $control_file
 	# reload
     start
 }