iocage starts jails with host environment variables

[Defenso-QTH]

My original use case:

• install a jail with a service that needs web access
• define http_proxy on the host
• iocage start testjail
• jail service does not work because the domains it uses are blocked by the proxy, although it is allowed to access them directly without proxy by firewall rules, and that is why the proxy is never actually configured inside the jail.

To confirm, I created a dummy rc.d script that dumps the environment on start with env >> /root/start_env.txt and I can see the http_proxy variable is defined inside.

I believe iocage start should always start jails in a clean environment to ensure they behave like regular FreeBSD systems, that have empty environments at boot unless explicitly configured otherwise.