Honor a user's "remember me" request on login.

The "rem" variable isn't being passed from POST_login()
to handle_login(), so the latter isn't aware of the
user's selecting the option.  This rectifies that.

r2/r2/controllers/api.py

@@ -630,6 +630,7 @@ class ApiController(RedditController):
             form=form,
             responder=responder,
             user=user,
+            rem=rem,
         ))
         return handle_login(**kwargs)