Removes EE differences

Moves EE code into EE file and
uses render_if_exists helper

app/views/projects/tree/_tree_header.html.haml

@@ -76,8 +76,7 @@
                       #{ _('New tag') }
 
 .tree-controls
-
-  = lock_file_link(html_options: { class: 'btn path-lock' })
+  = render_if_exists 'projects/tree/lock_link'
   = link_to s_('Commits|History'), project_commits_path(@project, @id), class: 'btn'
 
   = render 'projects/find_file_link'

ee/app/views/projects/tree/_lock_link.html.haml

+= lock_file_link(html_options: { class: 'btn path-lock' })