// Release lock when the metadata is verified, and reader
		// is ready to be read.
		//
		// This is possible to be lock free because
		// - xl.meta for inlined objects has already read the data
		//   into memory, any mutation on xl.meta subsequently is
		//   inconsequential to the overall read operation.
		// - xl.meta metadata is still verified for quorum under lock()
		//   however writing the response doesn't need to serialize