core:Upgrade - Error Can't start the ovirt-engine-dwhd service

Upgrade - Error Can't start the ovirt-engine-dwhd service

Adding a new varaible to dwh_history_timekeeping named
lastStatisticsUpdate.
This variable indicates when statistics on vm/vm interface/host/host
insterface/disk was changed.

Change-Id: I3461f0bf9ac30b8413179f32d50e017fca0cf777
Signed-off-by: Eli Mesika <emesika@redhat.com>
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=918152