core, engine: New validations for host entrance in clusters

* Prevents a host from entering in a cluster with a different
  CPU architecture;
* Reports an error if the cluster does not support the CPU of a
  host;

Change-Id: Ia617481b102b3d5383a0d38da03e10ff95afefe2
Signed-off-by: Vitor de Lima <vitor.lima@eldorado.org.br>