Fixes #2666: Uses correct function for displaying choices label

 * Changes record.length_type to record.get_length_type_display

netbox/dcim/tables.py

@@ -179,7 +179,7 @@ CABLE_TERMINATION_PARENT = """
 """
 
 CABLE_LENGTH = """
-{% if record.length %}{{ record.length }}{{ record.length_unit }}{% else %}—{% endif %}
+{% if record.length %}{{ record.length }}{{ record.get_length_unit_display }}{% else %}—{% endif %}
 """