Fix documented _output PATH for AWS

Actually, modifying your path shouldn't be necessary at all.  The `cluster/kubecfg.sh` and `cluster/kubectl.sh` should auto detect the os/platform and find a binary -- both for the binary release and the locally built option.

You can probably remove the PATH mangling from the entire file and simplify things.

Furthermore, those scripts should be able to call the EC2 API to find the IP of the master on each call.  With that you can skip the `export KUBERNETES_MASTER` line below also.

Give it a try and let me know if that works for you.