Fix slowdown in TAP tests due to recent walreceiver change.
Commit
05a7be93 changed the timing of the first reply sent by a
walreceiver, which caused a few TAP tests that call wait_for_catchup()
when they haven't actually streamed anything yet to wait ~10 seconds
(wal_receiver_status_interval).
Before commit
05a7be93 the initial reply was sent after 100ms, but
there's no reason not to send it immediately as a slight improvement.
Do the same for HS feedback for consistency.
Author: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://postgr.es/m/742545.
1668377284%40sss.pgh.pa.us