A previous commit added the capability to read the DNS configuration options
from a Windows host, while removing the capability to read from a resolv.conf-like
file.
This commit addresses this issue: if the given ``--resolv-conf`` option is not set to
``Host``, it will consider it as a file, preserving the previous behavior.
Currently, there are some unit tests that are failing on Windows due to
various reasons:
- getHostDNSConfig is reading a resolv.conf file. However, we don't have
that on Windows. Instead, we can get the DNS server list and the DNS
suffix list from Windows itself.
On Windows, getHostDNSConfig will now return the host's DNS configuration
if the given resolverConfig is "Host". If it's not "Host" or an empty string,
an error will be returned.
Based on the code from kubernetes/test/images/agnhost/dns/dns_windows.go
