501c35afff
Motivation: BinaryMemcacheObjectAggregator doesn't retain ByteBuf `extras`. So `io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1` will be thrown when aggregating a message containing `extras`. See the unit test for an example. Modifications: `ratain` extras to fix IllegalReferenceCountException. Result: `extras` is retained.