1. string is formatted as unsafe json. Since this is created on the fly;
TaintKey and Effect are formatted as a 'key=effect' instead of '{key=effect}'
eliminating unsafe json representation.
2. Adds a fail test case for the case where a taint with same key and effect is added
and removed together.
Manual Testing
```
▶ ./_output/bin/kubectl taint nodes kind-control-plane key1=:NoSchedule key1=:NoSchedule-
error: can not both modify and remove the following taint(s) in the same command: key1=NoSchedule
```
Kubernetes-commit: 1a3eda9394b7ff473434506f2756cc9df6288cea
Arda Güçlü
inosato
Manu Gupta
Clayton Coleman
clarklee92
Sean Sullivan