endless of client call in provider client

[armstrongli]

If the server response StatusUnauthorized error every time, the iterator will exhausting all the stack until overflow.

https://github.com/rackspace/gophercloud/blob/master/provider_client.go#L207

[armstrongli]

Fixed in PR: #622

[armstrongli]

After more investigation, I notice that the token got is not from client. It's from the options which parsed from the caller.
The result is that the token is override by the MoreHeaders which has the old, expired token.