Standardise some fields-when-empty in equipment rendering

Following previous commit to fix rendering locationless equipment, this standardises rendering of some empty fields (to use &amp;mdash; like other fields do). Checked on local install and rendering looks fine in various views. The only concern might be less obvious side-effects on scripting access, etc.
hostname is actually a required field of servermanagement. So that "if" is more correctly
{% if result.servermanagement %}