-Always unbind event if object isn't visible
-Use widget-specific refresh event for multi-edit actions, to prevent
other widgets from being refreshed unecessarily.
Show notice if no VMs are selected in port forwarding/load balancing
-- prevent server call from being performed and 'infinite list' from
being generated
Bug was caused by a 'cloudStack.fullRefresh' event being triggered on
a non-existent edit widget, for a non-existent project. I changed the
widget to only refresh if the current instance is visible (i.e., most
likely the user still has active data for it)