Set build update log level to debug
Set build update log level to debug

We get this a lot.  It's not helpful.

Change-Id: Icf0191ded019c705a42446269d647cb52843ef58
Reviewed-on: https://review.openstack.org/36733
Reviewed-by: Jeremy Stanley <98883b97e35b7bb1ac282bb863f2e9d917db0454@yuggoth.org>
Reviewed-by: Monty Taylor <37c07a49ee3d5191376d758eb1d8298b34456b8e@inaugust.com>
Approved: James E. Blair <e81a02a9d6405977f63a769d9f6ec8ed9d924325@inaugust.com>
Tested-by: Jenkins

wikimedia/integration-zuul,wikimedia/integration-zuul,devdattakulkarni/zuul_messaging,devdattakulkarni/zuul_messaging,wikimedia/integration-zuul,gooddata/zuul,wikimedia/integration-zuul,gooddata/zuul,gooddata/zuul,gooddata/zuul,devdattakulkarni/zuul_messaging,gooddata/zuul