conf: sampling: drop unused tunables

With the recent consolidation of disk stats
and added support for one-item sample windows,
a bunch of tunables has become obsolete.

These tunables were already unsupported, so
any configuration which was making use of
them was likely already broken,
so this patch just drops them.

Change-Id: I6066a2554b6208a8a3c6e09bcde15c21b66ed8d2
Signed-off-by: Francesco Romani <fromani@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34389
Reviewed-by: Dan Kenigsberg <danken@redhat.com>