Don't use private last_request variable

This is exposed in more recent versions of httpretty via a public method
rather than accessing it from the class.

Change-Id: I86949d94ac9b647ef577ee7db0ec4d664d6bc60b
Fix references to auth_token in middlewarearchitecture doc

The middlewarearchitecture doc was still referring to
keystone.middleware.auth_token, but the middleware was moved to
keystoneclient.

Also, corrected some other minor typos.

Change-Id: I270ea2ccc739596e99a4a852bff3b5b7d1c85c82
Merge "Don't use private last_request variable"
Merge "Fix references to auth_token in middlewarearchitecture doc"