We are using k8s 1.16, so we can enable PodOverhead alpha
feature for our testing.

Signed-off-by: Salvador Fuentes <salvador.fuentes@intel.com>

- Remove `Downward API` tests from the list of skipped tests.
  These tests pass when enabling the `PodOverhead` feature on
  kubernetes.
- Add a `Daemon set` test which requires to have a cluster
  with at least two nodes.

Fixes: kata-containers#2242.

Signed-off-by: Salvador Fuentes <salvador.fuentes@intel.com>

We need to lower the request of CPUs on the pod-number-cpu.yaml
which is used to run our CPU test. This is required as we now
have enabled PodOverhead and our CI VMs are small.

In addition, increase the sleep time that is run inside one of the
containers, so that we are sure that we can measure the number
of CPUs that it is using.

Signed-off-by: Salvador Fuentes <salvador.fuentes@intel.com>