Comment 4 for bug 1887165

Reviewed: https://review.opendev.org/740457
Committed: https://git.openstack.org/cgit/openstack/python-tripleoclient/commit/?id=2873dd4df62f104bef6a9ce36bdf5385b75b96b5
Submitter: Zuul
Branch: master

commit 2873dd4df62f104bef6a9ce36bdf5385b75b96b5
Author: Michele Baldessari <email address hidden>
Date: Fri Jul 10 15:19:45 2020 +0200

    Cleanup UndercloudHostsEntries

    When we update the UndercloudHostsEnries we basically
    take the output of 'getent hosts "$(hostname -s).ctlplane"'
    and push it into a parameter, so tripleo-ansible can
    make sure it adds the hostentry for the undercloud on
    the whole overcloud.

    The problem is that getent hosts can return multiple
    entries, which will then be injected into the parameter
    and then written into /etc/hosts. This contstantly adds the
    undercloud.ctlplane string and we end up adding it at
    everydeploy making it grow quadratically.

    This eventually leads to a too large json file and the deploys
    start failing with:
        heat.common.exception.RequestLimitExceeded:
          Request limit exceeded: JSON body size (4396634 bytes)
            exceeds maximum allowed size (4194304 bytes).

    Tested this by deploying an environment and then running
    a few redeploys to make sure that the undercloud entries
    in /etc/hosts on the undercloud itself do not grow at
    each redeploy.

    Change-Id: I37d75600825f48be9e15470cacba7b3a0371a3e2
    Closes-Bug: #1887165