Description:
  everywhere the NFS client uses the req_offset() function today, it adds
  req->wb_offset to the result.  this patch simply makes "+req->wb_offset"
  a part of the req_offset() function.

Test status:
  Passes all Connectathon '02 tests with v2, v3, UDP and TCP.  Passes
  NFS torture tests on an x86 UP highmem system.