--strict is meaningless when --revision is specified.

* tests/blackbox/test_push.py:
(load_tests): Switch to name based indirection following IRC chat
with lifeless, spiv and poolie.
(TestPushStrictWithChanges._changes_type): Now a string
(TestPushStrictWithChanges.setUp): Use getattr to call the right
bound method.
(TestPushStrict.make_local_branch_and_tree): Add one commit so we
have meat for push --revision.
(TestPushStrict.assertPushSucceeds): Add a pushed_revid parameter.
(TestPushStrictWithChanges.test_push_with_revision): New test.

* builtins.py:
(cmd_push.run): Don't look at --strict' when '--revision' is
specified.