Make ra serf properly parse lock timeouts installed by generic dav clients.

* subversion/libsvn_ra_serf/get_lock.c
  (locks_closed): Properly parse timout format. This is the actual fix.

* subversion/libsvn_ra_serf/lock.c
  (locks_closed): Properly parse timeout format from the server response of
    the LOCK requests.

* subversion/tests/cmdline/lock_tests.py
  (dav_lock_timeout): New test, creating timeout lock via http request.
  (test_list): Add test.

This issue was
Found by: Sergey Raevskiy <sergey.raevskiy{_AT_}visualsvn.com>
(but the patch from his mail doesn't fix the issue on trunk.
 It might have worked around the problem on 1.7.x and 1.8.x)


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1579588 13f79535-47bb-0310-9956-ffa450edef68