OSP13z9 update fails due to dumb-init not being installed

Issue

• During the OSP13 z9 controller update it was repeatedly failing and ultimately it was due to the dumb-init package not being installed on the controllers and computes. Once the package was installed 'Manually' the controller update finished successfully.

• The error messages do not make that immediately apparent with all of the rabbit and failed container messages. This is the error we grabbed from one of the controllers:

Nov 11 11:16:19 overcloud-controller-2 dockerd-current: time="2019-11-11T11:16:19.168928958-06:00" level=error msg="Handler for POST /v1.26/containers/8529699461b0b377e795e298f413296ba06351b7ca43cf2a1ba046d8138cff51/start returned error: oci runtime error: container_linux.go:235: starting container process caused \"exec: \\\"dumb-init\\\": executable file not found in $PATH\"\n"