Improve firewall service name check for < win2k8

On some versions of Windows, "operatingsystemversion" may return extra
information in the version string (such as preprending "Microsoft").
This commit fixes the module so that it will find the correct service
name on these versions.
Merge pull request #3 from supercow/os_version_to_regex

Improve firewall service name check for < win2k8