fixes #3138 . Update istatistics after operation is run and  before resp...

...onse is send to client
I thought that actual process is put/get/remove operations. And process (in this case put, get or remove) is done on the node, when we get to notify stage of client. We already did the put/get/remove just notification is left. And this way, I made sure that operation is done on the node, then statistics are updated on the node, then client gets the response.