raw_http_request was aliased to send_http_request, which is below the
level of the middleware being applied.

This patch makes raw_http_request behave like request, except the only
middleware that is applied is the AuthN for talking to the chef server
Add tests for raw_http_request to check that the authenticator gets
called and that the correct headers are passed to send_http_request
add a doc comment on the purpose of raw_http_request
Merge branch 'jc/OC-10471/raw_http_request'
CHEF-4715 and CHEF-4714