simplified pattern matching, fixed ungrouped (#22523)

* simplified pattern matching, fixed ungrouped

ungrouped was ignored for patterns, now it is usable again

* even simpler

(cherry picked from commit 273786d0bd)

lib/ansible/inventory/__init__.py

@@ -473,25 +473,16 @@ class Inventory(object):
         """
 
         results = []
-        hostnames = set()
 
         def __append_host_to_results(host):
-            if host.name not in hostnames:
-                hostnames.add(host.name)
+            if host.name not in results:
+                if not host.implicit:
                     results.append(host)
 
         groups = self.get_groups()
         for group in groups.values():
-            if pattern == 'all':
+            if self._match(group.name, pattern):
                 for host in group.get_hosts():
-                    if host.implicit:
-                        continue
-                    __append_host_to_results(host)
-            else:
-                if self._match(group.name, pattern) and group.name not in ('all', 'ungrouped'):
-                    for host in group.get_hosts():
-                        if host.implicit:
-                            continue
                     __append_host_to_results(host)
             else:
                 matching_hosts = self._match_list(group.get_hosts(), 'name', pattern)