Fix slowdown in TAP tests due to recent walreceiver change.

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