Disable our wrapping of the Django settings during migrations

This will hopefully get us past the unfortunate check against the
HostMetric table, which doesn't exist when you are upgrading from 3.8
to 4.x.

Additionally, guard against AUTH_LDAP_GROUP_TYPE not being in settings
for conf migration 0006.

awx/conf/apps.py

@@ -1,3 +1,5 @@
+import sys
+
 # Django
 from django.apps import AppConfig
 
@@ -12,6 +14,9 @@ class ConfConfig(AppConfig):
 
     def ready(self):
         self.module.autodiscover()
-        from .settings import SettingsWrapper
 
-        SettingsWrapper.initialize()
+        if not set(sys.argv) & {'migrate', 'check_migrations'}:
+
+            from .settings import SettingsWrapper
+
+            SettingsWrapper.initialize()

awx/conf/migrations/_ldap_group_type.py

@@ -5,7 +5,7 @@ from django.utils.timezone import now
 
 
 def fill_ldap_group_type_params(apps, schema_editor):
-    group_type = settings.AUTH_LDAP_GROUP_TYPE
+    group_type = getattr(settings, 'AUTH_LDAP_GROUP_TYPE', None)
     Setting = apps.get_model('conf', 'Setting')
 
     group_type_params = {'name_attr': 'cn', 'member_attr': 'member'}