…althy devices exist

In case of node reboot/kubelet restart, the flow of events involves
obtaining the state from the checkpoint file followed by setting
the `healthDevices`/`unhealthyDevices` to its zero value. This is
done to allow the device plugin to re-register itself so that
capacity can be updated appropriately.

During the allocation phase, we need to check if the resources requested
by the pod have been registered AND healthy devices are present on
the node to be allocated.

Also we need to move this check above `needed==0` where needed is
required - devices allocated to the container (which is obtained from
the checkpoint file) because even in cases where no additional devices
have to be allocated (as they were pre-allocated), we still need to
make sure he devices that were previously allocated are healthy.

Signed-off-by: Swati Sehgal <swsehgal@redhat.com>
(cherry picked from commit dc1a592)