Inventory: properly create groups with plurals:False (netbox-community#141)

Author: DouglasHeriot

plugins/inventory/nb_inventory.py

@@ -668,6 +668,10 @@ def add_host_to_groups(self, host, hostname):
             if not groups_for_host:
                 continue
 
+            # Make groups_for_host a list if it isn't already
+            if not isinstance(groups_for_host, list):
+                groups_for_host = [groups_for_host]
+
             for group_for_host in groups_for_host:
                 if self.group_names_raw:
                     group_name = group_for_host