kolla-ansible 15.6.0 release

meta:version: 15.6.0
meta:diff-start: -
meta:series: zed
meta:branch: stable/zed
meta:release-type: release
meta:pypi: no
meta:first: no
meta:release:Author: Bartosz Bezak <bartosz@stackhpc.com>
meta:release:Commit: Bartosz Bezak <bartosz@stackhpc.com>
meta:release:Change-Id: Iad00462b4eec7e22216153ec084ec24a1d2d9dc9
meta:release:Workflow+1: Dr. Jens Harbott <frickler@offenerstapel.de>
meta:release:Code-Review+2: Dr. Jens Harbott <frickler@offenerstapel.de>
meta:release:Code-Review+2: Elod Illes <elod.illes@est.tech>
meta:release:Code-Review+1: Michal Nasiadka <mnasiadka@gmail.com>