various jobs failing on repo setup/package install - limestone mirror issues

At [1][2][3] various jobs are failing in the gate, unable to download packages due to mirror issues. It seems to be specific to mirror.regionone.limestone.opendev.org and the trace looks like: (from [1])

 2021-06-15 02:33:20 | Errors during downloading metadata for repository 'delorean-current':
 2021-06-15 02:33:20 | - Curl error (28): Timeout was reached for http://mirror.regionone.limestone.opendev.org:8080/rdo/centos8-ussuri/component/tripleo/a5/6a/a56ab848c53f2f9c51bd13511f3b5d48094a8a34_adff45fe/repodata/repomd.xml [Operation too slow. Less than 1000 bytes/sec transferred the last 30 seconds]
 2021-06-15 02:33:20 | Error: Failed to download metadata for repo 'delorean-current': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

Not sure if the issue is ongoing or a one off issue but we've had problems with this particular mirror in the recent past (see [4]) and I was pinged (marios|ruck) about limestone issues yesterday so thought it best to file this bug for tracking

[1] https://504a6afcff55c8f91b0c-2937bb652abe1e5f0c19a6a7c68db9e1.ssl.cf5.rackcdn.com/796207/1/gate/tripleo-ci-centos-8-containers-multinode/3b786d2/logs/subnode-1/home/zuul/repo_setup.log
[2] https://storage.gra.cloud.ovh.net/v1/AUTH_dcaab5e32b234d56b626f72581e3644c/zuul_opendev_logs_752/796207/1/gate/tripleo-ci-centos-8-standalone-upgrade-ussuri/75236a3/logs/undercloud/home/zuul/repo_setup.log
[3] https://storage.bhs.cloud.ovh.net/v1/AUTH_dcaab5e32b234d56b626f72581e3644c/zuul_opendev_logs_e0d/795019/2/gate/tripleo-ci-centos-8-content-provider/e0d29df/job-output.txt
[4] https://bugs.launchpad.net/tripleo/+bug/1929461