Merge pull request #62657 from matthyx/master

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Update all script shebangs to use /usr/bin/env interpreter instead of /bin/interpreter

This is required to support systems where bash doesn't reside in /bin (such as NixOS, or the *BSD family) and allow users to specify a different interpreter version through $PATH manipulation.
https://www.cyberciti.biz/tips/finding-bash-perl-python-portably-using-env.html
```release-note
Use /usr/bin/env in all script shebangs to increase portability.
```

Kubernetes-commit: b5f61ac129019d314e473584c1491b7ca62144c7

vendor/k8s.io/client-go/tools/clientcmd/client_config.go

@@ -27,7 +27,6 @@ import (
 	"github.com/golang/glog"
 	"github.com/imdario/mergo"
 
-	"k8s.io/api/core/v1"
 	restclient "k8s.io/client-go/rest"
 	clientauth "k8s.io/client-go/tools/auth"
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"
@@ -338,7 +337,7 @@ func (config *DirectClientConfig) Namespace() (string, bool, error) {
 	}
 
 	if len(configContext.Namespace) == 0 {
-		return v1.NamespaceDefault, false, nil
+		return "default", false, nil
 	}
 
 	return configContext.Namespace, false, nil