Update repository head successively during project update

It prevents situation when async worker slowly updates HEAD and we show
old branch as repository HEAD in project settings
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/contexts/projects/update_context.rb

@@ -10,13 +10,7 @@ module Projects
       new_branch = params[:project].delete(:default_branch)
 
       if project.repository.exists? && new_branch != project.default_branch
-        GitlabShellWorker.perform_async(
-          :update_repository_head,
-          project.path_with_namespace,
-          new_branch
-        )
-
-        project.reload_default_branch
+        project.change_head(new_branch)
       end
 
       project.update_attributes(params[:project], as: role)

app/models/project.rb

@@ -472,4 +472,9 @@ class Project < ActiveRecord::Base
   def visibility_level_field
     visibility_level
   end
+
+  def change_head(branch)
+    gitlab_shell.update_repository_head(self.path_with_namespace, branch)
+    reload_default_branch
+  end
 end