One of the TAP tests added in 923def9a53 did not wait after creating a
subscription, and wait_for_catchup is not sufficient for this. So if the
tablesync workers happen do not complete quickly enough, the test won't
see the expected results.
This probably explains intermittent failures on a couple buildfarm
animals (komodoensis, petalura and snapper).
Reported-by: Tom Lane
Discussion: https://postgr.es/m/170549.1648330634@sss.pgh.pa.us
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