LU-14603 ptlrpc: quiet messages for unsupported opcodes

LU-14603 ptlrpc: quiet messages for unsupported opcodes

Reduce message spew for unhandled RPC opcodes.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I35496168e3aa29ecb06076654ef0aa97ba2540e5
Reviewed-on: https://review.whamcloud.com/43257
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Stephane Thiell <sthiell@stanford.edu>
Reviewed-by: Oleg Drokin <green@whamcloud.com>