Revision 1449428

In the tree conflict tests, enable testing with an incoming file
replacement.  For 'switch', don't test with incoming replacements because
'switch' ignores ancestry in its libsvn_repos difference calculation (unlike
'update') and so does not notice replacements.

Eliminate two helper functions, in the interest of clarity.

[Note from the future: In r1449413 'switch' was fixed to not ignore ancestry
by default, and in r1450582 these tests were updated to test incoming
replacements with 'switch'.]

* subversion/tests/cmdline/tree_conflict_tests.py
  (f_rpls): Enable testing with an incoming file replacement.
  (ensure_tree_conflict): Make the 'commit_local_mods' parameter optional.
  (test_tc_up_sw, test_tc_merge): Delete.
  (...elsewhere...): Call ensure_tree_conflict() directly. Don't test
    'switch' with incoming replacements.