Use PostBodyTask for admin config endpoint

[ScottG489]

PostBodyTask is more appropriate for the admin config endpoint used to do live updates to the applications config (currently only job limit config). The current config update endpoint only accepts GET requests. However, we are updating the config so a POST request is what's appropriate.

Look into this Task to fully evaluate if this is the better use case and then implement it.

Also refer to email "Regarding updating the dropwizard config on runtime" and see if we can give credit to the email's sender for letting me know about this Task.