Enable ServerGroup scheduler filters by default

The Icehouse release includes a server group REST API. For these
groups to actually function properly, the server group scheduler
filters must be enabled. So, these filters should be enabled by
default since the API is also enabled by default. If the API is not
used, the scheduler filters will be a no-op.

DocImpact
Change-Id: Ia52d7fcfff52377d8beae2acd9b7eba9c6c74e09
Closes-bug: #1303983
(cherry picked from commit 7b8402ed3ba734836119441bdf1a6d6c661c8df2)