Fix race in 032_relfilenode_reuse.pl.
Add wait_for_catchup() call to the test added by commit
e2f65f42. Per
slow build farm animal grison.
Also fix a comment.
Discussion: https://postgr.es/m/CA%2BhUKGLJ2Vy8hVQmnYotmTaEKZK0%3D-GcXgNAgcHzArZvtS4L_g%40mail.gmail.com