core: added support for ksm settings

Since vdsm 3.3 the ksm is controlled via MoM and there should
be a way to control the ksm settings from the engine. This patch
adds the initial support to the engine core.

Change-Id: I719d0b130fda26894db9fdaf892fd6da28bb648b
Bug-Url: https://bugzilla.redhat.com/1026980
Signed-off-by: Jiri Moskovcak <jmoskovc@redhat.com>