Implement this method for updating the configuration of a given group
the implementation should update the passed in config object with appropriate changes if for
any reason config can't be updated. throw a RuntimeException stating the reason.
group - the name of the group to update cluster config for
config - the configuration object, never null
configObject - the return value of CommandResult.getConfigObject. CommandResult is the
return value of your command method.
a boolean indicating whether a change to the cluster configuration was persisted.