Check for errors when trying to create the auth token file (kubernete…

…s-retired#447)

* Check for errors when trying to create the auth token file
* Close the file right away, instead of closing with `defer`

The file is not being used after it's created/opened, so there's no
reason to defer the closing.

core/controlplane/config/token_config.go

@@ -156,7 +156,11 @@ func ReadOrEncryptAuthTokens(dirname string, encryptor CachedEncryptor) (*Encryp
 
 	// Auto-creates the auth token file, useful for those coming from previous versions of kube-aws
 	if _, err := os.Stat(authTokenPath); os.IsNotExist(err) {
-		os.OpenFile(authTokenPath, os.O_RDONLY|os.O_CREATE, 0600)
+		file, err := os.OpenFile(authTokenPath, os.O_RDONLY|os.O_CREATE, 0600)
+		if err != nil {
+			return nil, err
+		}
+		file.Close()
 	}
 
 	if _, err := ReadRawAuthTokens(dirname); err != nil {