Don't create a default pid file (#637)

modules/setting/setting.go

@@ -515,12 +515,10 @@ please consider changing to GITEA_CUSTOM`)
 		}
 	}
 
-	if len(CustomPID) == 0 {
-		CustomPID = CustomPath + "/run/app.pid"
+	if len(CustomPID) > 0 {
+		createPIDFile(CustomPID)
 	}
 
-	createPIDFile(CustomPID)
-
 	if len(CustomConf) == 0 {
 		CustomConf = CustomPath + "/conf/app.ini"
 	}