make add ticket links a local modal

app/assets/javascripts/app/controllers/ticket_zoom.js.coffee

@@ -688,6 +688,7 @@ class TicketSidebar extends App.Controller
           object_type: 'Ticket'
           object:      ticket
           links:       @links
+          container:   @el.closest('.content')
         )
 
     showTicketHistory = =>

app/assets/javascripts/app/controllers/widget/link.js.coffee

@@ -83,6 +83,7 @@ class App.WidgetLink extends App.Controller
       link_object_id: @object.id
       object:         @object
       parent:         @
+      container:      @container
     )
 
 class App.LinkAdd extends App.ControllerModal