Follow-up to r16285: fix test failure over ra_dav.
Follow-up to r16285: fix test failure over ra_dav.

* subversion/tests/clients/cmdline/lock_tests.py
  (unlock_already_unlocked_files): Allow the error messages actually produced
  by ra_dav.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@856375 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion