Add an XFAIL regression test for a file external problem introduced in r1448345.
The test succeeds if the first change made in r1448345 is reverted.

Reported by: <GezwiZ> in #svn IRC

* subversion/tests/cmdline/externals_tests.py
  (update_deletes_file_external, test_list): New test.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1600311 13f79535-47bb-0310-9956-ffa450edef68