Merge branch 'fix-impersonate-ui' into 'master'

Remove impersonate token from flash scope in UI

See merge request gitlab-org/gitlab-ce!17480

app/controllers/admin/impersonation_tokens_controller.rb

@@ -9,7 +9,6 @@ class Admin::ImpersonationTokensController < Admin::ApplicationController
     @impersonation_token = finder.build(impersonation_token_params)
 
     if @impersonation_token.save
-      flash[:impersonation_token] = @impersonation_token.token
       redirect_to admin_user_impersonation_tokens_path, notice: "A new impersonation token has been created."
     else
       set_index_vars