Bug 1059131 — Merge /session and /fxa-oauth/params
Make POST /fxa_oauth/params to always return a new Hawk Session and to reject existing Hawk Session.
@mnoorenberghe feedback.
Use getOauthHawkSession for all /fxa-oauth endpoints.
Merge pull request #199 from mozilla-services/1059131-fxa-session

Bug 1059131 — Merge /session and /fxa-oauth/params