Clarify broker_krb_service_name documentation

broker_krb_service_name is prefxied with 'HTTP/' string and used by mod_auth_krb
where as bind_krb_principal is expected to be the full principal name. We could
normalize those two but for now just document the proper use.
Allow client certs to be read by apache
Merge pull request #365 from andrewklau/mcollective_ssl

Allow client certs to be read by apache
Merge pull request #364 from sdodson/docs-broker_krb_service_name

Clarify broker_krb_service_name documentation