py3: update the python3-whitelist with new tests which pass on Python 3

We have now 34 tests passing on Python 3.

contrib/python3-whitelist

@@ -1,11 +1,34 b''
 test-ancestor.py
+test-backwards-remove.t
+test-branch-tag-confict.t
+test-casecollision.t
+test-check-commit.t
 test-check-execute.t
+test-check-pyflakes.t
+test-check-pylint.t
 test-check-shbang.t
 test-contrib-check-code.t
 test-contrib-check-commit.t
 test-ctxmanager.py
+test-diff-issue2761.t
+test-diff-reverse.t
+test-diff-subdir.t
+test-dirstate-nonnormalset.t
 test-doctest.py
+test-empty-dir.t
+test-excessive-merge.t
+test-issue1089.t
+test-issue1993.t
+test-issue842.t
+test-locate.t
 test-lrucachedict.py
+test-manifest.py
+test-merge-default.t
+test-merge-subrepos.t
+test-merge2.t
+test-merge5.t
+test-revlog-packentry.t
 test-run-tests.py
 test-unified-test.t
+test-update-reverse.t
 test-xdg.t