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

Simplify hostname configuration test, including using
worker.waitForServiceState().

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