Make upgrade_tests.py:upgrade_1_7_dir_external work with exclusive
working copy locking.

* subversion/libsvn_wc/wc_db_wcroot.c
  (svn_wc__db_wcroot_parse_local_abspath): Don't abandon an open sdb.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1572200 13f79535-47bb-0310-9956-ffa450edef68