engine, webadmin: Edit Approve Host popup -> Cluster not updated

The host cluster is not updated in the
"Edit Approve Host" dialog.

For oVirt node the cpu flags is null, so
GetHostArchitectureQuery throws a NPE.

When cpu flags is null, ArchitectureType.unknown
is returned and the webadmin displays all clusters
for data center if unknown is returned.

Change-Id: I4b0357f07de5ac27902ceb250b7ef4c2e1642d08
Bug-Url: https://bugzilla.redhat.com/1056998
Signed-off-by: Ravi Nori <rnori@redhat.com>