Following up on r1554019, pass the right baton value in the pre-http-v2 commit
logic.

* subversion/libsvn_ra_serf/commit.c
  (checkout_node): Pass pointer to handler instead of pointer to pointer.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1556974 13f79535-47bb-0310-9956-ffa450edef68