The motivation for this commit is that these two test fail on systems
that have different Name Service Switch configuration settings. A
concrete example of this is when using Red Hat Enterprise Linux (RHEL)
7.

If Name Service Switch is available on the operating system then it
might be configured differently (/etc/nsswitch.conf).
If the system is configured with no dns the error code will be
AI_AGAIN, but if there are more services after the dns entry, for
example some linux distributions skip a myhostname service by default
which would still produce the ENOTFOUND error.

This commit suggests checking for either ENOTFOUND or EAI_AGAIN to
accommodate systems like the ones described above. The references below
indicate that others have run, or are running, into this aswell.

Refs: nodejs#12075
Refs: nodejs/help#687

The hosts configuration on a system can affect how dns look up works and
different error can occur with different setups. This commit adds a
check for EAI_AGAIN to avoid the issue reported in the issue referred to
below.

Refs: nodejs#15825