netflow: avoid db corruption by stopping service; closes #1017

Inspired by: @adschellevis

src/etc/rc.backup_netflow

@@ -9,6 +9,10 @@ if [ "${1}" == "restore" ]; then
 	fi
 else
 	if [ -d "${BACKUPDIR}" ]; then
+		/usr/local/etc/rc.d/flowd_aggregate stop
 		tar -C / -czf "${BACKUPFILE}" "${BACKUPDIR}"
+		if [ "${1}" == "stop" ]; then
+			/usr/local/etc/rc.d/flowd_aggregate start
+		fi
 	fi
 fi

src/etc/rc.halt.subr

@@ -10,9 +10,9 @@
 /usr/local/etc/rc.opnsense stop
 
 # backup volatile internals
-/usr/local/etc/rc.backup_dhcpleases
-/usr/local/etc/rc.backup_netflow
-/usr/local/etc/rc.backup_rrd
+/usr/local/etc/rc.backup_dhcpleases stop
+/usr/local/etc/rc.backup_netflow stop
+/usr/local/etc/rc.backup_rrd stop
 
 # wait for config lock to release
 php -a >/dev/null  << EOF