Due to recent infrastructure changes, infra began using port 8088. This
caused a conflict with our apache config, causing services to not start.
Infra is changing this port (Ie67bbba02dbf61a481f66001de3e0dede9448316)
but it may take up to a week to take effect.

Instead of having our gate broken for a week, I'm changing the default
port. 3928 was not chosen at random; it's listed as the netboot-pxe
service port in /etc/services.

Change-Id: Ibb635555dc516e54f8d46e2dba0f9cecfa5dd1b3
Closes-bug: 1590139
Co-Authored-By: John L. Villalovos <john.l.villalovos@intel.com>
(cherry picked from openstack/ironic commit
2898b622f7072995b0c778d2a762adba5afe75aa)