Enable attach/detach operations to storage manager

Attaching volume is currently not possible from within the list of cloud
volumes of a chosen storage manager because the handler in `ems_common`
does not have a path for the button (even though attach/detach option is
enabled).

This patch adds the missing handlers and redirects to the required
`cloud_volume` controller.

app/controllers/ems_common.rb

@@ -454,6 +454,10 @@ def button
       javascript_redirect :controller => "cloud_tenant", :action => "edit", :id => find_checked_items[0]
     elsif params[:pressed] == "cloud_volume_new"
       javascript_redirect :controller => "cloud_volume", :action => "new", :storage_manager_id => params[:id]
+    elsif params[:pressed] == "cloud_volume_attach"
+      javascript_redirect :controller => "cloud_volume", :action => "attach", :id => find_checked_items[0]
+    elsif params[:pressed] == "cloud_volume_detach"
+      javascript_redirect :controller => "cloud_volume", :action => "detach", :id => find_checked_items[0]
     elsif params[:pressed] == "cloud_volume_edit"
       javascript_redirect :controller => "cloud_volume", :action => "edit", :id => find_checked_items[0]
     elsif params[:pressed].ends_with?("_edit") || ["#{pfx}_miq_request_new", "#{pfx}_clone",