Summary: https://phorge.dev.yugabyte.com/D38644 only works for systemd version 240 and up when append was added to StandardOutput. This diff fixes the systemd log to only be set for the correct versions.

Test Plan: install YBA on ubuntu20 and centos7

Reviewers: dshubin, sanketh

Reviewed By: dshubin

Subscribers: yugaware

Differential Revision: https://phorge.dev.yugabyte.com/D38761