Fix adding branch as protected to not allow pushing to it (#2556)

* Fix adding branch as protected to not allow pushing to it

* Fix can_push value to false in protected_branch (#2560)

* Fix integration test

models/migrations/v43.go

@@ -0,0 +1,18 @@
+// Copyright 2017 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"code.gitea.io/gitea/models"
+
+	"github.com/go-xorm/xorm"
+)
+
+func fixProtectedBranchCanPushValue(x *xorm.Engine) error {
+	_, err := x.Cols("can_push").Update(&models.ProtectedBranch{
+		CanPush: false,
+	})
+	return err
+}