Add ability to fetch restored glacier object

[kjmkznr]

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The restored Glacier object has been excluded from loading because the storage class remains Glacier. This fix will load the Glacier object if it has already been restored.

• Restored object's HeadObject response example

{
    "Restore": "ongoing-request=\"false\", expiry-date=\"Sun, 13 Aug 2017 00:00:00 GMT\"",
    ...
    "StorageClass": "GLACIER",
    "Metadata": {}
}

• Ongoing restore object's HeadObject response example

{
    "Restore": "ongoing-request=\"true\"",
    ...
    "StorageClass": "GLACIER",
    "Metadata": {}
}