Resolve issue #3378, by using a bit more of the WC-NG power. We now only
delete locks when switching to a new location.

This makes the original locks re-appear when switching back to the original
location.

* subversion/libsvn_wc/update_editor.c
  (close_file): Don't delete locks when switching.

* subversion/tests/cmdline/lock_tests.py
  (lock_multi_wc): New test, verify (un)locking of paths in multiple WCs at
    one. (Issue #3105)
  (locks_stick_over_switch): Verify lock handling during switching.
    (issue #3378)


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1436694 13f79535-47bb-0310-9956-ffa450edef68