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

An internal error when wrong cluster id is passed
causing incomplete error message.

Change-Id: If54bcf4ab325d607c869bb8aec609718c15e8b26
Bug-Url: https://bugzilla.redhat.com/890469
Signed-off-by: Ravi Nori <rnori@redhat.com>