get_machine_ips took too long to complete

[norman shen]

Description
===========

I found that get_machine_ips could took too long before returning IP addresses. There are
around 160 instances with about 200 nics which results in around 1000 network adapters on the host.
calling netifaces.ifaddresses approximately took around 0.2 ~ 0.5 seconds.

Steps to reproduce
==================

1. use an arm64 host or host load is high
2. booting 200 instances with neutron hybird SG driver enabled
3. reboot nova-compute

Expected result
===============

get_machine_ips should take no more than 2 seconds to return

Actual result
=============

Took around 500 seconds

Environment
===========
1. phyitum arm64 as compute node

[Artom Lifshitz (notartom)]

This ran a bell for me, so I went digging, and found [1]. I'm not sure we can make get_machine_ips() take less time with a reasonable amount of error (some sort of parallelism or scatter/gather type thing seems like overkill here), but we can probably make the _check_my_ip() check at libvirt startup optional and configurable, since it only prints a warning.

[1] https://review.opendev.org/c/openstack/nova/+/671471