UHS fails initial sync if YK scheduler has not finished startup

[richscott]

If the K8S cluster has just started up, and the Yunikorn scheduler is still finishing its setup, starting the UHS service immediately may result in an initial-sync error (YK partitions not found) - UHS retry the initial-sync 2 or 3 times, with a 10 second interval sleep - we may want to make the retries and sleep interval configurable in the UHS config file.