* fix: Make --reverse tests with --blockcount or --bytes actually terminate.
Note that these options still don't really give intuitive results, because
the ending conditions are evaluated on the client, which then needs to
convey to the server via the control channel to stop sending. This
will almost never result in the desired outcome of "a test of exactly
N sends (or bytes) sent from the server to the client".
Also add test cases for --blockcount / --bytes with --reverse.
Towards #982.
