aodh charm does not have nrpe relation

[Xav Paice]

I would like to use NRPE/Nagios to monitor aodh units, but there's currently no nrpe-external-master relation available.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/757720

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-aodh/+/757720
Committed: https://opendev.org/openstack/charm-aodh/commit/fbb77776382890b2b9aa68369f234c5a899b047e
Submitter: "Zuul (22348)"
Branch: master

commit fbb77776382890b2b9aa68369f234c5a899b047e
Author: Xav Paice <email address hidden>
Date: Tue Oct 13 15:50:22 2020 +1300

    Add NRPE checks for services

    Adds the nrpe-external-master layer and checks for services managed by
    this charm.

    func-test-pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/445

    Change-Id: I9109078bb0d07159de2024cb836d659a533e50c7
    Closes-Bug: #1750486