Fixes #6357 - taxonomy_added is not defined while selecting/updating user's taxonomy

This fixes the problem with javascript and users. I've seen the trick used in compute_resource_vms (javascript for the Virtual Machine tab is loaded through Host#new, trends, etc.. 

However there is one case that intrigues me a bit, javascript nfs_visibility in Media _form is loaded through the form only and it works in the two-pane view.