cloud restore: completing read through

cloud restore: completing read through

What are all supported :

* It allows read-through for cloud-tiered objects via restore_obj_from_cloud
* New tier config options user need to set allow_read_through to true and
  read_through_restore_days more than 1 for this feature to work, also
  objects with retain_head_object will be available for this feature.
* First get request will fail with restoring in progress error, objects
  are downloaded asynchronously.
* The objects restore are temporary.
* Tested `aws s3api get-object`, `aws s3api head-object` and `aws s3 cp`

In addition send timeout errors for first readthrough request

Also addressed lint warning and other cleanup(review comments)

Signed-off-by: Jiffin Tony Thottan <thottanjiffin@gmail.com>