Add new style instance group scheduler filters

Prior to Icehouse, there was a different type of handling of the
'group' scheduler hint that got lost in the completion of the server
groups API.  This patch completes the code necessary to provide
backwards compatibility with the old behavior.

Previously, the policy for groups was simply based on what scheduler
filters you had enabled.  You could have either the affinity or
anti-affinity filter enabled and that would be applied to all groups.
These filters now act on groups with a policy type of 'legacy'.

New filters have been added that can be enabled simultaneously and act
based on the policy set on the group via the server group API.

DocImpact

Change-Id: Ia65c151396415ca48725cb3c756f33efa01d2fe5
Closes-bug: #1296913
Merge "Add new style instance group scheduler filters"