core, engine: Avoid migration in ppc64

This patch forces every ppc64 VM to be pinned to a host and every ppc64
cluster to have the "Do not migrate" resilience policy.

Change-Id: I4808f3e91ccf37462727a28d35f9f9faae1dfd6c
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1057178
Signed-off-by: Gustavo Pedrosa <gustavo.pedrosa@eldorado.org.br>