Memcached server should throw error when stats comes with args

Memcached protocol says https://github.com/memcached/memcached/blob/master/doc/protocol.txt:

"stats <args>\r\n

Depending on <args>, various internal data is sent by the server. The
kinds of arguments and the data sent are not documented in this vesion
of the protocol, and are subject to change for the convenience of
memcache developers."

Hence, we don't support <args> passed to stats. So, on one side, http://community.jboss.org/docs/DOC-14644
needs to be updated in order to indicate the fact that this is not supported.

And the other hand, if someone passes <args>, we should throw an server error (or client error rather?)
indicating that <args> is not supported. For sure, the entire line needs to be read.