minikube kubectl appends --cluster flag breaking exec commands

[bkeelan]

Looks like #10535 may have introduced a bug

[minikube] ~ $ minikube kubectl -- --context minikube exec ambassador-84ffc9fdc4-nxp4h -- echo "hello"
hello --cluster minikube

[minikube] ~ $ kubectl --context minikube exec ambassador-84ffc9fdc4-nxp4h -- echo "hello"
hello

This causes issues when trying to run exec commands because the --cluster flag is always appended to the end leading to issues such as

[minikube] ~ $ minikube kubectl -- --context minikube exec mysql-db-79b945965d-gtzf7 -- mysqladmin ping

mysqladmin: [ERROR] unknown option '--cluster'
command terminated with exit code 2

[minikube] ~ $ minikube version
minikube version: v1.18.1
commit: 09ee84d530de4a92f00f1c5dbc34cead092b95bc

[afbjorklund]

I have noticed this as well, ever since the introduction of that extra -- in exec.

kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.