Migrate check_host util to Pkg::Util::Net

One by one, we're going to remove *all* utils from 00_utils.rake and move them
into classes. This continues that work with 'check_host'.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Migrate 'remote_ssh_cmd' to Pkg::Util::Net

One by one I want to migrate these utilities over to the libraries while I have
a quiet moment or two. Here's another one.