Don't modify parameter for port
Don't modify parameter for port

When passing in a port, our string-ifying helper function was modifying the variable if it happened to be an array, using `map!`. This changes to make a copy of the array instead of modifying it directly.

Fixes #120.

itmustbejj/firewall,itmustbejj/firewall,opscode-cookbooks/firewall,williamsjj/firewall,opscode-cookbooks/firewall,williamsjj/firewall,chef-cookbooks/firewall,chef-cookbooks/firewall