nut: initscripts hotplug: Fix many small semantic issues

Small but important tweaks to fix the operation of the nut initscripts
and hotplug scripts.  All hail shellcheck and proofreading and
dogfooding.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>

net/nut/files/nutshutdown

@@ -4,11 +4,6 @@
 # See /LICENSE for more information.
 #
 
-. /lib/functions.sh
-
-mount -o remount,ro /overlay /overlay
-mount -o remount,ro / /
-
 stop_instance() {
 	/etc/init.d/nut-server stop "$1"
 }
@@ -16,29 +11,39 @@ stop_instance() {
 shutdown_instance() {
 	local cfg="$1"
 	config_get driver "$cfg" driver "usbhid-ups"
+
 	# Only FSD if killpower was indicated
 	if [ -f /var/run/killpower ]; then
-		/lib/nut/${driver} -a "$cfg" -k
+		/lib/nut/"${driver}" -a "$cfg" -k
 	fi
 }
 
-if [ -f /var/run/killpower ]; then
-	if [ -f /etc/config/nut_server ]; then
-		config_load nut_server
+do_fsd() {
+	if [ -f /var/run/killpower ]; then
+		# Only make FS readonly if we are doing an FSD
+		mount -o remount,ro /overlay /overlay
+		mount -o remount,ro / /
 
-		# Can't FSD unless drivers are stopped
-		config_foreach stop_instance driver
-		# Driver will  wait 'offdelay' before shutting down
-		config_foreach shutdown_instance driver
-		# So this can happen
-		poweroff
-		# And just in case
-		sleep 120
-		# Uh-oh failed to poweroff UPS
-		reboot -f
+		. ${IPKG_INSTOOT}/lib/functions.sh
+
+		if [ -f /etc/config/nut_server ]; then
+			config_load nut_server
+
+			# Can't FSD unless drivers are stopped
+			config_foreach stop_instance driver
+			# Driver will  wait 'offdelay' before shutting down
+			config_foreach shutdown_instance driver
+			# So this can happen
+			rm -f /var/run/killpower
+			poweroff
+			# And just in case
+			sleep 120
+			# Uh-oh failed to poweroff UPS
+			reboot -f
+		else
+			poweroff
+		fi
 	else
 		poweroff
 	fi
-else
-	poweroff
-fi
+}