On 1.8.x-r1579588 branch: adjust new test to avoid FAIL.

* subversion/tests/cmdline/lock_tests.py
  (dav_lock_timeout): Tweak expected error.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/1.8.x-r1579588@1588325 13f79535-47bb-0310-9956-ffa450edef68