test_bucket_list_prefix_basic and test_bucket_list_prefix_delimiter_basic needed bypass

Hi,
I found out that the prefix response is not decoded back in the field of prefix when using `list_objects`.
As you probably know when using boto3 the client sets automatically the encoding type url (see https://github.com/boto/boto3/issues/816):

> “Encoding type is automatically set because there are unicode characters which can break the XML parser. To work around the issue, we automatically set the encoding type parameter to url if the customer hasn't already set it. We then decode the keys on the way back, again only if we provided that parameter.”

That why is needs to decode the fields back. I found out that the prefix response is not decoded back in the field of a prefix when using `list_objects`, I opened boto3 an [issue](https://github.com/boto/boto3/issues/3534) about it, but until they fix it we can use a bypass for the problematic line:
`eq(response['Prefix'], 'foo/')`

I suggest that we will decode `response['Prefix'] `and insert a comment so that it will be clear that it is just a bypass.
This case when using the `list_objects` with prefix, appears in 2 tests: test_bucket_list_prefix_basic and test_bucket_list_prefix_delimiter_basic