Fixed issue with freebsd package provider current_installed_version

The regular expression that was being used to determine the installed version
would get tripped up when the package name included regular expression
characters.  EX: bonnie++

Since the package_name string is available using slice to extract the version
string from pkg_info avoids regular expressions complexity.
Fixed issue with freebsd package provider port_path.

port_path was also using a regular expression that didn't handle +'s in the
package_name.  Changed this to use split to avoid any issues with package_name
that contains any regular expression characters.
rspec tests to cover CHEF-4371
Per review changed both instances of the code in question to regexs