Small refactoring of modules/private (#15947)

* Use correct variable name.

* doer is never nil here.

* Use status code constants.

* Replaced generic map with concrete struct.

* Fixed windows lint.

* Removed unused method.

* Changed error codes.

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

modules/private/serv.go

@@ -58,7 +58,6 @@ type ServCommandResults struct {
 // ErrServCommand is an error returned from ServCommmand.
 type ErrServCommand struct {
 	Results    ServCommandResults
-	Type       string
 	Err        string
 	StatusCode int
 }