LU-12523 ptlrpc: Stop sending ptlrpc_body_v2

LU-12523 ptlrpc: Stop sending ptlrpc_body_v2

ptlrpc_body_v2 does not include space for jobids, that
means that when we added jobid to the RPC debug messages,
we started getting errors like this:

LustreError: 6817:0:(pack_generic.c:425:lustre_msg_buf_v2()) msg
000000005c83b7a2 buffer[0] size 152 too small (required 184, opc=-1)

This happened every time we tried to print a ptlrpc_body_v2
message.

body_v2 is still sent on some RPCs for compatibility with
very old versions of Lustre, but we no longer support
interop with those versions (latest reported is 2.3).

So, stop sending ptlrpc_body_v2 on any RPCs.

Note that we need to retain the ptlrpc_body_v2 definitions
and parsing capability for interop with servers which still
use them for some messages, which is all prior to this
patch.

One further note:
This does *not* fix the case of newer clients collecting
rpctrace with older servers.  They will still see the
error message for some RPCs.  That could be fixed with
tweaks to the debug printing code.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: I54fc9a174788235c43fe9101a1b42adc7f547847
Reviewed-on: https://review.whamcloud.com/35583
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>