core: Add selinux host info to VdsDynamic

Added the SELinux enforce mode of the host, as reported by vdsm.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=894084
Change-Id: If472f68702b59280c721450d4db50dc27dc19a30
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>