update Host manager to handle Query Sets

* filter_host_string now returns a query set instead of Q(). This change
updates the Host manager to remove the .filter() call since the results
returned from filter_host_string() has already turned Q() -> Query Set

awx/main/managers.py

@@ -41,7 +41,7 @@ class HostManager(models.Manager):
                     # If we don't disable this, a filter of {'inventory': self.instance} gets automatically
                     # injected by the related object mapper.
                     self.core_filters = {}
-                    return qs.filter(q)
+                    return qs & q
         return qs