On fsfs-lock-many branch: extend test.

* subversion/tests/libsvn_fs/locks-test.c
  (lock_multiple_paths): Test both force and unforced unlock.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsfs-lock-many@1572641 13f79535-47bb-0310-9956-ffa450edef68