[bug 1408967] Set CSRF middleware after session middleware.
[bug 1408967] Set CSRF middleware after session middleware.

glogiotatidis/snippets-service,mozmar/snippets-service,mozilla/snippets-service,mozmar/snippets-service,mozilla/snippets-service,mozmar/snippets-service,mozilla/snippets-service,glogiotatidis/snippets-service,glogiotatidis/snippets-service,mozmar/snippets-service,glogiotatidis/snippets-service,mozilla/snippets-service