hooks: Adding hooks for ovirt-node-upgrade

Currently ovirt-node offers ovirt-node-upgrade tool to
upgrade node images. This patch adds the pre-upgrade
script for vdsm tasks before the upgrade.

Change-Id: I986fe6edb8f5619dcbca33cccab080245654fd02
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1079087
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>