Followup on r1537415: Put the bogus path back in the slash separated format.

* subversion/mod_dav_svn/mod_dav_svn.c
  (dav_svn__translate_name): Not that much harder to just combine the
    two without the helpers.  During dev of the original change I switched
    from apr_psprintf() to apr_pstrcat() which makes the NULLs ok, so the
    only issue is avoiding a trailing slash.  Switch back to NULL from
    SVN_VA_NULL so the change can be backported.  A separate commit after this
    will restore that.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1537555 13f79535-47bb-0310-9956-ffa450edef68