### Please describe the problem.

Creating a remote for a GCS durable reduced availability (DRA) or nearline bucket fails with "Invalid argument".

### What steps will reproduce the problem?

    $ git annex initremote test encryption=none bucket=BUCKET type=S3 host=storage.googleapis.com

This works if BUCKET is a standard bucket, but fails with "invalid argument" if BUCKET is a DRA or nearline bucket.

### What version of git-annex are you using? On what operating system?

git-annex version: 5.20150205
on macos 10.10

### Please provide any additional information below.

I spent some time in strace, and my best guess is that this is because git-annex is sending x-amz-storage-class: STANDARD.  I couldn't figure out a way to disable this; if I did e.g.

    $ git annex initremote test encryption=none bucket=BUCKET type=S3 host=storage.googleapis.com storageclass="NEARLINE"

it still fails and still sends storage-class: STANDARD.  I also tried storageclass="" -- same thing.

Here's the HTTP request that's failing:

    PUT /annex-uuid HTTP/1.1\r\nAuthorization: AWS GOOG<...>:<...>=\r\nDate: Mon, 16 Mar 2015 01:41:38 GMT\r\nHost: jlebar-backup-annex-nearline-test.storage.googleapis.com\r\nContent-Type: \r\nx-amz-storage-class: STANDARD\r\nContent-Length: 36\r\n\r\n<...>

And the (rather unhelpful) HTTP response:

    HTTP/1.1 400 Bad Request\r\nContent-Type: application/xml; charset=UTF-8\r\nContent-Length: 117\r\nVary: Origin\r\nDate: Mon, 16 Mar 2015 01:41:38 GMT\r\nServer: UploadServer      (\"Built on Feb 27 2015 12:13:16 (1425067996)\")\r\nAlternate-Protocol: 80:quic,p=0.5\r\n\r\n<?xml version='1.0' encoding='UTF-8'?><Error><Code>InvalidArgument</Code><Message>Invalid argument.</ Message></Error>

[[!format sh """

$ AWS_ACCESS_KEY_ID=... AWS_SECRET_ACCESS_KEY="..." git annex --debug initremote test encryption=none bucket=<DRA bucket> type=S3 host=storage.googleapis.com
[2015-03-15 19:12:19 PDT] read: git ["--git-dir=.git","--work-tree=.","show-ref","git-annex"]
[2015-03-15 19:12:19 PDT] read: git ["--git-dir=.git","--work-tree=.","show-ref","--hash","refs/heads/git-annex"]
[2015-03-15 19:12:19 PDT] read: git ["--git-dir=.git","--work-tree=.","log","refs/heads/git-annex..d7640d68e3bd55735fb275816df0b94ec05031a7","-n1","--pretty=%H"]
[2015-03-15 19:12:20 PDT] chat: git ["--git-dir=.git","--work-tree=.","cat-file","--batch"]
initremote test (checking bucket...) git-annex: S3Error {s3StatusCode = Status {statusCode = 400, statusMessage = "Bad Request"}, s3ErrorCode = "InvalidArgument", s3ErrorMessage = "Invalid argument.", s3ErrorResource = Nothing, s3ErrorHostId = Nothing, s3ErrorAccessKeyId = Nothing, s3ErrorStringToSign = Nothing}

# End of transcript or log.
"""]]
