Multiple delete fails to delete objects with key containing 2+ subsequent space characters [JIRA: RCS-191]

[shino]

2015-04-28 Update: Changed subject to indicate the bug of list objects API. Multiple delete API itself does no bad. Some tools like s3cmd issues list objects before multiple delete to grab keys, so such tools are affected.

Confirmed at version 2.0.0, probably 1.5.x are affected too.

Steps:

% s3cmd -c .s3cfg.15018.alice mb s3://test3
Bucket 's3://test3/' created
% s3cmd -c .s3cfg.15018.alice put tools.mk s3://test3/'three   spaces'
tools.mk -> s3://test3/three   spaces  [1 of 1]
 5751 of 5751   100% in    0s   418.06 kB/s  done
% s3cmd -c .s3cfg.15018.alice ls s3://test3/
2015-04-24 02:57      5751   s3://test3/three   spaces
% s3cmd -c .s3cfg.15018.alice del -r -f s3://test3/
File s3://test3/three   spaces deleted
% s3cmd -c .s3cfg.15018.alice ls s3://test3/
2015-04-24 02:57      5751   s3://test3/three   spaces

Expected output from the final step (s3cmd ls) is empty, but
there was one.

From the output of console debug log from multiple detele path,
sebsequnt spaces became corrupted to single space:

11:57:36.407 [debug] deleting keys at <<"test3">>: [<<"three spaces">>]

zd://10707

[shino]

Spaces are trimmed at XML parsing [1], which was introduced by [2] fixing other bug.

The function is called by:

./riak_cs_wm_user.erl:143:    case riak_cs_xml:scan(Body) of
./riak_cs_wm_user.erl:160:    case riak_cs_xml:scan(Body) of
./riak_cs_wm_object_upload_part.erl:212:        {ok, ParsedData} = riak_cs_xml:scan(Body),
./riak_cs_s3_response.erl:335:    {ok, ParsedData} = riak_cs_xml:scan(Xml),
./riak_cs_wm_bucket_delete.erl:161:    case riak_cs_xml:scan(Body) of
./riak_cs_acl_utils.erl:305:    case riak_cs_xml:scan(Xml) of

[1] https://github.com/basho/riak_cs/blob/develop/src/riak_cs_xml.erl#L69
[2] #795