Additional fix for regression introduced in edcb7a8 with does not propagate the HTTP proxy config to OAuth anymore

Propagating fix to refreshToken() which was also impacted. Moved the propagation of the request factory into the createResourceOwnerPasswordAccessTokenProvider() method.  It was hard/verbose to unit test this with little added value. I'll rather complete the integration test which is still on my todo list.
Merge pull request #86 from Orange-OpenSource/oauth-proxy-fix-2

Additional fix for oauth proxy regression