Add validation for ChaosExperiment's NodeSelector Node Availability

[rahulchheda]

FEATURE REQUEST

• Need to add validation check for configmaps listed under ChaosEngine ('spec.Experiments[*].NodeSelector[*].Name), in the cluster.
• We need to check the status of Node, with taints (if exist).
• For reference on how to define the function around this, PTAL at this PR Description: https://github.com/litmuschaos/admission-controllers/pull/10

Tracking this here: litmuschaos/litmus#2182

What happened:

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

[vivekab]

when I was going through spec.Experiments[*].NodeSelector[*].Name I'm not able to find the NodeSelector probably because the vendor(chaos-operator) is not updated. when I try to update the vendor I get the error from that says k8s.io/api go: github.com/litmuschaos/chaos-operator upgrade => v0.0.0-20210218040724-2ae60b66f001 go get: github.com/litmuschaos/chaos-operator@v0.0.0-20210218040724-2ae60b66f001 requires github.com/operator-framework/operator-sdk@v0.15.2 requires k8s.io/apiextensions-apiserver@v0.0.0: reading k8s.io/apiextensions-apiserver/go.mod at revision v0.0.0: unknown revision v0.0.0
any suggestion how can I solve this?