DD_HISTOGRAM_AGGREGATES and DD_HISTOGRAM_PERCENTILES take comma-separated values, not space-separated

[chrisjseaton]

See descriptions of variables in the readme -- both claim "separated by spaces"

Additional environment details (Operating System, Cloud provider, etc):
datadog/docker-dd-agent:12.7.5321-jmx

Steps to reproduce the issue:

1. set DD_HISTOGRAM_AGGREGATES=max median avg count sum and start the agent

Describe the results you received:

No histograms pushed via dogstatsd. head /var/log/datadog/collector.log in the container gives:

2019-03-21 15:26:31 UTC | WARNING | dd.collector | config(config.py:306) | Ignored histogram aggregate
max median avg count sum, invalid

Describe the results you expected:

Histograms pushed with the given aggregates.

Additional information you deem important (e.g. issue happens only occasionally):

Workaround is to give a comma-separated list.

[adz]

FYI This is similarly incorrectly described over here:
https://docs.datadoghq.com/agent/docker/?tab=standard#dogstatsd-custom-metrics