proxy: fix startup on /var memory disk

src/opnsense/scripts/proxy/setup.sh

+#!/bin/sh
+
+SQUID_DIRS="/var/log/squid /var/run/squid /var/squid /var/squid/cache /var/squid/logs"
+
+for SQUID_DIR in ${SQUID_DIRS}; do
+	mkdir -p ${SQUID_DIR}
+	chown -R squid:squid ${SQUID_DIR}
+	chmod -R 750 ${SQUID_DIR}
+done
+
+/usr/local/sbin/squid -z

src/opnsense/service/conf/actions.d/actions_proxy.conf

 [start]
-command:/usr/local/sbin/squid -z;/usr/local/etc/rc.d/squid start
+command:/usr/local/opnsense/scripts/proxy/setup.sh;/usr/local/etc/rc.d/squid start
 parameters:
 type:script
 message:starting proxy