Drop max-servers to 40 for tripleo HP region.

Currently we only have 40 testenvironments and with the sustained
backlog of reviews this can lead to cascade failure (normally the
slight excess gains efficiency by allowing
building/deleting/copying-logs jobs to be doing that while 40 or so
active jobs use testenvs. We'll re-up it once the overload is gone.

Change-Id: Id7332c1d341aa48deae49576839d12b6fdf36b68