[ec2] Use user_data if specified (#54494)

* Use user_data if specified

* changelog

changelogs/fragments/54494-ec2-user-data.yaml

@@ -0,0 +1,3 @@
+bugfixes:
+  - ec2 - Only use user_data if the user has specified a value.
+    This prevents setting the instance's user data to b'None'.

lib/ansible/modules/cloud/amazon/ec2.py

@@ -1070,8 +1070,9 @@ def create_instances(module, ec2, vpc, override_count=None):
                       'placement': zone,
                       'instance_type': instance_type,
                       'kernel_id': kernel,
-                      'ramdisk_id': ramdisk,
-                      'user_data': to_bytes(user_data, errors='surrogate_or_strict')}
+                      'ramdisk_id': ramdisk}
+            if user_data is not None:
+                params['user_data'] = to_bytes(user_data, errors='surrogate_or_strict')
 
             if ebs_optimized:
                 params['ebs_optimized'] = ebs_optimized