Remove the editor v2 shims from the to be removed svnmucc editor driver. This
also removes an unneeded ra session that is never really used except for v2
debugging.

* subversion/svnmucc/svnmucc.c
  (fetch_baton): Remove struct.
  (fetch_base_func): Remove function.
  (fetch_props_func): Remove function.
  (fetch_kind_func): Remove function.
  (get_shim_callbacks): Remove function.
  (execute): Remove unneeded ra session, shims, etc.
    Use primary ra session to check if we should move up a level.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1550846 13f79535-47bb-0310-9956-ffa450edef68