Since I901184cb1a4b6eb0d6fa6363bc6ffbcaa0c9d21d in Kilo the
aggregates information about a HostState object (which is a
wrapper over a ComputeNode) is cached in the scheduler, so the
comments in the scheduler evolution doc about not accessing the
aggregates table in the DB from filters/weighers and such is
extremely out of date and should just be removed.
Change-Id: Ibcbad227813d3b37b4e314eddbf3bae6e85652ea
Related-Bug: #1820283