Fix upstart error

Fixing upstart error:

==> proxy: Error: Execution of '/usr/sbin/update-rc.d squid3 defaults' returned 1: update-rc.d: /etc/init.d/squid3: file does not exist
==> proxy: Error: /Stage[main]/Squid3/Service[squid3_service]/enable: change from false to true failed: Execution of '/usr/sbin/update-rc.d squid3 defaults' returned 1: update-rc.d: /etc/init.d/squid3: file does not exist