system groups - minor mods for pull request comments

this commit contains a few minor mods to address comments received
during pull request

src/app/controllers/system_errata_controller.rb

@@ -68,7 +68,6 @@ def install
     render :text => task.task_status.uuid
   rescue Exception => error
     errors error
-    Rails.logger.error error.backtrace.join("\n")
     render :text => error, :status => :bad_request
   end
 

src/app/controllers/system_group_errata_controller.rb

@@ -61,7 +61,6 @@ def install
     render :text => job.pulp_id
   rescue Exception => error
     errors error
-    Rails.logger.error error.backtrace.join("\n")
     render :text => error, :status => :bad_request
   end
 

src/app/views/activation_keys/_system_groups.html.haml

@@ -1,14 +1,14 @@
-= content_for :title do
+= content_for(:title) do
   #{@activation_key.name}
 
-= content_for :remove_item do
+= content_for(:remove_item) do
   - if editable
     = link_to _("Remove Activation Key"), activation_key_path(@activation_key.id), :confirm => _('Are you sure?'), :method => :delete, :class=>"remove_item", :remote=>true
 
-= content_for :navigation do
+= content_for(:navigation) do
   = render_menu(1..2, activation_keys_navigation)
 
-= content_for :content do
+= content_for(:content) do
   #system_groups
     %table
       %thead

src/app/views/systems/_system_groups.html.haml

@@ -1,6 +1,6 @@
 = render :partial => "system_tupane_header_nav"
 
-= content_for :content do
+= content_for(:content) do
   #system_groups
     %table
       %thead