Bump Kubernetes to v1.20.2

Bump Kubernetes to v1.20.2

The branch 1.20 in infra/stack/kubernetes is created from the commit
3f7a6e0 on master which is a combination of various updates. [0]

The later commits on master branch make adaptations for rook and ceph
causing deployments on baremetal to fail so they are not included on
1.20 branch.

They need to be done in a controlled manner without breaking baremetal
deployments if possible.

[0] https://gerrit.nordix.org/c/infra/stack/kubernetes/+/7781

Change-Id: Iac2da682f639d2177b10162db95cd796fb3124e6