When a change is reverted we send two emails:
1. one email for the creation of the revert change
2. one email for posting a message on the change that is reverted
The second email should contain the Change-Id of the change on which the
message is posted (and not the Change-Id of the newly created revert
change).
Add a test to verify that both emails are triggered as expected.
Change-Id: I34ec258a0f63fed82c67f181542b29ef280a72b4
Signed-off-by: Edwin Kempin <ekempin@google.com>