(#7224) Reword 'hostname was not match' error message

This error message is grammatically incorrect and unhelpful, so we replace it
with a message that explains more correctly what went wrong and what was
expected. This message happens when making an authenticated connection to a
server where the certificate doesn't match its hostname. This happens in the
REST terminuses, so we wrap their HTTP methods with a helper that will catch
the appropriate SSLError and re-raise it with the better message stating the
hostname used, and the list of hostnames that we were expecting it to be a part
of.

Unfortunately, because the certificate in question isn't available at error
time, we have to use the Net::HTTP#verify_callback to capture it.

Paired-With: Jacob Helwig <jacob@puppetlabs.com>
Reviewed-By: Dominic Maraglia <dominic@puppetlabs.com>