Merge pull request #50639 from simo5/setheader

Automatic merge from submit-queue (batch tested with PRs 50023, 50639)

Extend SetHeader Requests method ito accept multiple values

This allows to set headers that are multivalued directly.
The headers variable is not directly accessible and currently
SetHeaders allows to set only one value.

```release-note
NONE
```

staging/src/k8s.io/client-go/rest/request.go

@@ -322,11 +322,14 @@ func (r *Request) setParam(paramName, value string) *Request {
 	return r
 }
 
-func (r *Request) SetHeader(key, value string) *Request {
+func (r *Request) SetHeader(key string, values ...string) *Request {
 	if r.headers == nil {
 		r.headers = http.Header{}
 	}
-	r.headers.Set(key, value)
+	r.headers.Del(key)
+	for _, value := range values {
+		r.headers.Add(key, value)
+	}
 	return r
 }