Unset variables before evaluating options (avoid conflicts with environment variables)

[cstsw]

Before the arguments to the script are evaluated all variables that are used in the subsequent control flow are unset (in order to avoid conflicts with corresponding variables defined in the environment already, see #78).

[Codelica]

Systems like OPNSense have HOST set which can be very confusing. :) Hope this gets in. Until then env -i ./ssl-cert-check ...