Don't log RandAddSeedPerfmon details

Summary:
These are hard to deal with, as in a follow-up this function can get
called before the logging infrastructure is initialized.

Partial Backport of Core PR14955
https://github.com/bitcoin/bitcoin/pull/14955/commits/2d1cc5093949f8ea9487a68724162c8b39035ad8

Depends on D4387

Test Plan:

make check

Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Reviewed By: jasonbcox, O1 Bitcoin ABC, #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D4389