Move diff and wait to perform_action (#375)

This primarily moves the diff and wait logic from the various service
methods to perform_action to eliminate code duplication. I also moved
the diff_objects function out of the service object and moved most of
the find_resource logic to a new resource client method. We ended up
with several modules creating a service object just to use one of these
methods, so it seemed to make sense to make these more accessible.

tests/unit/module_utils/test_client.py

@@ -43,7 +43,10 @@ _temp_files = []
 
 def _remove_temp_file():
     for f in _temp_files:
-        os.remove(f)
+        try:
+            os.remove(f)
+        except FileNotFoundError:
+            pass
 
 
 def _create_temp_file(content=""):