engine : incomplete error when trying to add host with wrong cluster ID

Fix error message when trying to add host with wrong cluster ID using
ovirt-shell or api.

This patch fixes the format of the error message from "., -" to "., ".

The incomplete error message could not be reproduced, works for me.

Change-Id: I65f35c1fda1e36e6b05735424297c1f81d920553
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=890469
Signed-off-by: Ravi Nori <rnori@redhat.com>