[agent] 'info' command does not output NTP offset on later releases of datadog/docker-dd-agent

[saj]

How to reproduce:

Invoke /etc/init.d/datadog-agent info in a running datadog/docker-dd-agent container. I was able to reproduce on the image tagged with 12.6.5251.

Observed output:

(Trimmed for clarity.)

====================
Collector (v 5.25.1)
====================

[...]

  Clocks
  ======

    NTP offset: Unknown ([Errno -8] Servname not supported for ai_socktype)
    System UTC time: 2018-07-09 12:18:36.667921

[...]

  Checks
  ======

[...]

    ntp (1.2.0)
    -----------
      - Collected 0 metrics, 0 events & 0 service checks

I think this bug is directly related to a similar bug filed against integrations-core:

• NTP check broken: Servname not supported for ai_socktype (missing /etc/services from netbase) integrations-core#1569 (bug report)
• https://github.com/DataDog/integrations-core/pull/1633/files (patch)

The agent implements its own NTP query and did not benefit from the patch linked above.

This problem is mostly cosmetic -- it does not affect the behaviour of the ntp check.