Automatic merge from submit-queue
update taints e2e, restrict taints operation with key, effect
Since taints are now unique by key, effect on a node, this PR is to restrict existing taints adding/removing/updating operations in taints e2e.
Also fixes https://github.com/kubernetes/kubernetes/issues/31066#issuecomment-242870101
Related prior Issue/PR #29362 and #30590