Ignore `daemonset-controller-hash` label key in federation before comparing the federated object with its cluster equivalent.

Kubernetes daemonset controller writes a daemonset's hash to the object
label as an optimization to avoid recomputing it every time. Adding a
new label to the object that the federation is unaware of causes
problems because federated controllers compare the objects in
federation and their equivalents in clusters and try to reconcile them.
This leads to a constant fight between the federated daemonset
controller and the cluster controllers, and they never reach a stable
state.

Ideally, cluster components should not update an object's spec or
metadata in a way federation cannot replicate. They can update an
object's status though. Therefore, this daemonset hash should be a
field in daemonset's status, not a label in object meta. @janetkuo says
that this label is only a short term solution. In the near future, they
are going to replace it with revision numbers in daemonset status. We
can then rip this bandaid out.