core: Display error when kdump detection enabled, but not configured

Display error after host status was changed to Up when kdump detection is
enabled for host, but fence_kdump is not configured properly
(configuration status is updated during getVdsCaps).

Change-Id: Iecf53614d4ac9cf08bf1df5ee69f4082083c1101
Bug-Url: https://bugzilla.redhat.com/1079821
Signed-off-by: Martin Perina <mperina@redhat.com>