Set the API version when checking differences in containers and use this to determine the location of the Memory value depending on the version used.

In v1.18 and earlier it was ['Config']['Memory'], but in v1.19 it
changed to ['HostConfig']['Memory'].

lib/ansible/modules/cloud/docker/docker.py

@@ -970,6 +970,9 @@ class DockerManager(object):
         running = self.get_running_containers()
         current = self.get_inspect_containers(running)
 
+        #Get API version
+        api_version = self.client.version()['ApiVersion']
+
         image = self.get_inspect_image()
         if image is None:
             # The image isn't present. Assume that we're about to pull a new
@@ -1038,6 +1041,10 @@ class DockerManager(object):
 
             actual_mem = container['HostConfig']['Memory']
 
+            #Use v1.18 API and earlier Memory element location
+            if docker_api_version <= 1.18:
+                actual_mem = container['Config']['Memory']
+
             if expected_mem and actual_mem != expected_mem:
                 self.reload_reasons.append('memory ({0} => {1})'.format(actual_mem, expected_mem))
                 differing.append(container)