LU-11644 ptlrpc: show target name in req_history

LU-11644 ptlrpc: show target name in req_history

Currently the req_history tracing shows the "self" NID as the second
field.  However, this is not very useful since there may be a number
of different targets on the same server, and since the logs are all
collected directly on the server we already know the local NID.

Instead of printing the "self" NID, store the target name as the
second field, if that is available, so that we can determine which
target the RPC was intended for.  This makes it easier to debug
problems with bad clients and isolate traffic for a specific target.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I4ce5b7c557c5b491bfe3bbc5ae80257f0a3ebbe5
Reviewed-on: https://review.whamcloud.com/37193
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>