Follow-up to r1529676: Update SASL-related code as well.

* subversion/svnserve/cyrus_auth.c
  (cyrus_auth_request): adapt to recent server baton change

* subversion/svnserve/serve.c
  (auth_request): ditto

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1529708 13f79535-47bb-0310-9956-ffa450edef68