tests: check some edge cases in bundle reordering tests

tests: check some edge cases in bundle reordering tests

While testing BundleReorderTest, I felt like adding more test cases to
check if reordering is touching only the right patches on the bundle.

This increases the number of patches on the test bundle to 5, and
changes the code to do the following tests:

- Reorder all patches
- Reorder only the first 3 patches
- Reorder only the last 3 patches
- Reorder only the middle 3 patches
- On all above tests, check if the 'order' field on the BundlePatch
  objects is still consistent

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>