Fix a bug introduced by new omniauth-oauth2 (1.4.0)
Fix a bug introduced by new omniauth-oauth2 (1.4.0)

This basically reverts the commit recently introduced on the Oauth2
omniauth gem here:

https://github.com/intridea/omniauth-oauth2/pull/70
https://github.com/intridea/omniauth-oauth2/commit/26152673224aca5c3e918bcc83075dbb0659717f

The callback_url in the base omniauth gem includes the query string so
by removing the overridden version the query string was being included
which was making Doorkeeper complain about a callback URL not being
equal.

watermarkchurch/wcc-auth