Following up on r1538519, don't make a function work in an unsupported scenario,
but make the caller skip the call to this function and its directory sibling.

* subversion/libsvn_wc/diff_editor.c
  (svn_wc__diff_local_only_file): Revert r1538519 change.

* subversion/libsvn_wc/diff_local.c
  (diff_status_callback): Don't call the diff local functions if the local node
    is deleted.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1538574 13f79535-47bb-0310-9956-ffa450edef68