docs: re-add instructions on setting wal_level for rsync use

Bruce Momjian <bruce@momjian.us>

Commit: 95a231aef9bb872913f67f30a8cffcfefaf8ca51
Author: Bruce Momjian <bruce@momjian.us>
Date: 2017-09-20T13:36:19Z
Releases: 9.6.6
docs:   re-add instructions on setting wal_level for rsync use

This step was erroneously removed four days ago by me.

Reported-by: Magnus via IM

Backpatch-through: 9.5

Files

PathChange+/−
doc/src/sgml/ref/pgupgrade.sgml modified +3 −1

Documentation touched