host-deploy: appropriate message for kdump detection

1. a system that does not support kdump is expected, so it cannot
   be warning.

2. messages with '!' are not polite, user did not do anything to
   justify that.

Change-Id: Ie10ebdbbc0b5148e4cd6e1b2deb251f96a2f56c7
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>