Get rid of the "nfscl: consider increasing kern.ipc.maxsockbuf"
message that was generated when doing experimental NFS client
mounts. I put that message in because the krpc would hang with
the default size for mounts that used large rsize/wsize values.
Since the bug that caused these hangs was fixed by r213756,
I think the message is no longer needed.

MFC after: 2 weeks