This adds the optional configuration options:
- statsd_host
- statsd_port
- statsd_metric_prefix (defaults to inventory_hostname)
- statsd_default_sample_rate
- statsd_sample_rate_factor
Which can be defined under swift globally or on the server level.
The configuration will only be added if statsd_host is defined.
Change-Id: I793b189e0a1f5ca4fc1fe17b1d89f2a83af8c796