Preserve state passed in to authorize_params

I know there's a lot of work being done that directly impacts the state logic, so this PR might be DOA, but I wanted to get the tests green.

Right now the authorize_params method is overwriting any state value passed into it with a randomly generated value.  This is seemingly contrary to the intention of the method, is definitely contrary to the intention expressed in the OAuth 2 spec, and causes several tests to fail.

This minor change preserves a passed in state value if it is present.  It also gets the tests running green.