Fixes site group lookup by using the correct key (#872)

Netbox returns the group association via a `group` key rather than a `site_group` key. This code erroneously looks for `site_group` which will always fail.

Author: hisham-vaporio

plugins/inventory/nb_inventory.py

@@ -995,9 +995,9 @@ def get_region_for_site(site):
         self.sites_region_lookup = dict(map(get_region_for_site, sites))
 
         def get_site_group_for_site(site):
-            # Will fail if site does not have a site_group defined in NetBox
+            # Will fail if site does not have a group defined in NetBox
             try:
-                return (site["id"], site["site_group"]["id"])
+                return (site["id"], site["group"]["id"])
             except Exception:
                 return (site["id"], None)