tests: os: config-json: cleanup persistentLogging test
tests: os: config-json: cleanup persistentLogging test

Minor cleanup of persistentLogging configuration test. Additionally,
reduce the reboot count to one to save time.

Change-type: patch
Signed-off-by: Joseph Kogut <461476587780aa9fa5611ea6dc3912c146a91760@balena.io>
resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin,resin-os/meta-resin