Fix: Header not propagated from adapater to client (#1532)
Fix: Header not propagated from adapater to client (#1532)

Bug: The header is not propagated from adapter to client Oauth2
result: reddit reponse 429 too many request.
https://www.reddit.com/r/redditdev/comments/3qbll8/429_too_many_requests/
lukeburden/django-allauth,rsalmaso/django-allauth,bittner/django-allauth,pztrick/django-allauth,pztrick/django-allauth,pztrick/django-allauth,rsalmaso/django-allauth,joshowen/django-allauth,AltSchool/django-allauth,rsalmaso/django-allauth,wli/django-allauth,spool/django-allauth,spool/django-allauth,joshowen/django-allauth,lukeburden/django-allauth,bittner/django-allauth,AltSchool/django-allauth,joshowen/django-allauth,pennersr/django-allauth,pennersr/django-allauth,AltSchool/django-allauth,wli/django-allauth,wli/django-allauth,bittner/django-allauth,pennersr/django-allauth,lukeburden/django-allauth,spool/django-allauth