engine: Block moving host with QoS to older cluster

This patch blocks the possibility of moving a host from a cluster that
supports Host Network QoS to one that doesn't, if any of the host's
network interfaces have any QoS capping on them.

Change-Id: I697617fcb943590f2437add7591a81a0b3a0cf3b
Bug-Url: https://bugzilla.redhat.com/1054322
Signed-off-by: Lior Vernia <lvernia@redhat.com>