Comment 5 for bug 1674732

Reviewed: https://review.openstack.org/449198
Committed: https://git.openstack.org/cgit/openstack/tripleo-image-elements/commit/?id=7e5e4dc029198d46705c2e8a4f3f3a06899ab450
Submitter: Jenkins
Branch: master

commit 7e5e4dc029198d46705c2e8a4f3f3a06899ab450
Author: Kambiz Aghaiepour <email address hidden>
Date: Thu Mar 23 11:34:15 2017 -0400

    51-hosts fails if given lots of changes

    The issue is how awk is used to update hosts files. When
    os-apply-config produces sufficiently large amounts of lines
    to be added (or ensure in) hosts files, awk will error out.
    To work around it, instead use sed, and reconstruct the
    host file(s) to ensure the entries between the comment delimeters
    of "# HEAT_HOSTS_START" and "# HEAT_HOSTS_END" are swapped with
    the new entries.

    Also get rid of blank lines produced by os-apply-config

    Partial-Bug: #1674732
    Change-Id: Ibe0a9f6ec10d55750e3b0e16301236141f988d69