caps: Add selinux enforcement reporting.

Added selinux field to getVdsCaps() what currently contains the mode of
enforcement of the host

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=894084
Change-Id: I98e0fcb71e831a76c4584bca46dc58fc4298180f
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/26951
Reviewed-by: Dan Kenigsberg <danken@redhat.com>