Use RDO Proxy mirror instead of centos mirrors

[chandan kumar]

https://logserver.rdoproject.org/openstack-periodic-integration-main/opendev.org/openstack/tripleo-ci/master/periodic-tripleo-centos-8-buildimage-ironic-python-agent-master/1e47a4d/build.log

```
2021-03-31 08:37:36.725 | dlrn-master-build-deps 2.0 MB/s | 464 kB 00:00
2021-03-31 08:37:37.305 | Advanced Virtualization mirror 0.0 B/s | 0 B 00:00
2021-03-31 08:37:37.306 | Errors during downloading metadata for repository 'advanced-virtualization':
2021-03-31 08:37:37.306 | - Curl error (7): Couldn't connect to server for http://mirror.centos.org/centos/8/virt/x86_64/advanced-virtualization/repodata/repomd.xml [Failed to connect to mirror.centos.org port 80: Connection refused]
2021-03-31 08:37:37.314 | Error: Failed to download metadata for repo 'advanced-virtualization': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried
2021-03-31 08:37:37.444 |
```

Many times our job got failed due to failed to download metadata from centos mirrors.

RDO already have mirror: http://mirror.regionone.vexxhost.rdoproject.org/centos/8/

Let's use that one in periodic and avoid these issues.

[chandan kumar (chkumar246)]

@dpwalik is checking with #centos team to whitelist the rdo mirror.

[chandan kumar (chkumar246)]

https://logserver.rdoproject.org/openstack-periodic-integration-main/opendev.org/openstack/tripleo-ci/master/periodic-tripleo-centos-8-buildimage-ironic-python-agent-master/1e47a4d/yum.repos.d/delorean-master-testing.repo

[advanced-virtualization]
name=Advanced Virtualization mirror
baseurl=http://mirror.centos.org/centos/8/virt/$basearch/advanced-virtualization/
gpgcheck=0
enabled=1
module_hotfixes=1

[centos-rabbitmq-38]
name=Messaging RabbitMQ
baseurl=http://mirror.centos.org/centos/8/messaging/$basearch/rabbitmq-38
gpgcheck=0
enabled=1
module_hotfixes=1
skip_if_unavailable=1

[centos-opstools]
name=opstools
baseurl=http://mirror.centos.org/centos/8/opstools/$basearch/collectd-5/
gpgcheck=0
enabled=1
module_hotfixes=1

[centos-nfv-ovs]
name=NFV SIG OpenvSwitch
baseurl=http://mirror.centos.org/centos/8/nfv/$basearch/openvswitch-2/
gpgcheck=0
enabled=1
module_hotfixes=1

[chandan kumar (chkumar246)]

https://review.opendev.org/c/openstack/tripleo-ci/+/784057 proposed a review to handle it in tripleo-ci job side.

[Alan Pevec (apevec)]

tl;dr from #centos-devel

> people should use mirrorlist and not point to mirror.c.o
> donated machines come and go

<ykarel> Arrfab, 173.214.244.24 is one of the failing ip
<Arrfab> ykarel: that one was removed and is *not* in DNS .. so check your own resolver that doesn't obey TTL either
<ykarel> Arrfab, ok will check, btw when it was removed?
<Arrfab> yesterday
<ykarel> okk so it matches our failure times

<Arrfab> you can query pdns{1..3}.centos.org for mirror.centos.org and none is answering that old/removed ip. so wondering if your resolver doesn't obey TTL and keep longer in cache

> in /etc/resolv.conf the system has 1.1.1.1, 8.8.8.8
> you can query with "dig @pdns1.centos.org mirror.centos.org +short"
> and same for pdns2/pdns3

[Alan Pevec (apevec)]

Reported as https://pagure.io/centos-infra/issue/270
but real fix is to change jobs to use local AFS mirrors (patch in comment 3)

We will also need to modify delorean-deps.repo to use mirrorlist and then adjust role which set AFS mirrors, simple s|http://mirror.centos.org/centos|$NODEPOOL_CENTOS_MIRROR|g will then not work!

[Marios Andreou (marios-b)]

adding a note here as there is a relevant issue happening with the dlrn builds https://bc407b42c3b88557b3de-7f9926fbce5c6ae120812541a1c87ecd.ssl.cf1.rackcdn.com/795788/1/check/tripleo-ci-centos-8-content-provider/aa18ad1/logs/delorean_logs/component/tripleo/7d/ea/7dea661f697eeda50ccd53ceda49bdbd415177f8_dev/root.log.txt.gz

"DEBUG util.py:596: Errors during downloading metadata for repository 'advanced-virtualization':
DEBUG util.py:596: - Curl error (28): Timeout was reached for http://mirror.centos.org/centos/8-stream/virt/x86_64/advancedvirt-common/repodata/repomd.xml [Connection timed out after 30000 milliseconds]
DEBUG util.py:596: Error: Failed to download metadata for repo 'advanced-virtualization': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

we can use this bug for digging into that as well (use local mirrors for the delorean builds) but it has a low priority at the moment as it seems this was a one-off otherwise the job looks OK @ https://zuul.opendev.org/t/openstack/builds?job_name=tripleo-ci-centos-8-content-provider today

[Alan Pevec (apevec)]

afaik we moved all CI jobs to use local AFS mirrors