nfsd4: kill unnecessary same_name() in setclientid_confirm

If conf and unconf are both found in the lookup by cl_clientid, then
they share the same cl_clientid.  We always create a unique new
cl_clientid field when creating a new client--the only exception is the
"probable callback update" case in setclientid, where we copy the old
cl_clientid from another clientid with the same name.

Therefore two clients with the same cl_client field also always share
the same cl_name field, and a couple of the checks here are redundant.

Thanks to Simon Holm Thøgersen for a compile fix.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: Simon Holm Thøgersen <odie@cs.aau.dk>