nfs: abstract out code needed to complete a sillyrename
The async rename code is currently "polluted" with some parts that are
really just for sillyrenames. Add a new "complete" operation vector to
the nfs_renamedata to separate out the stuff that just needs to be done
for a sillyrename.
Signed-off-by: Jeff Layton <jlayton@redhat.com> Tested-by: Anna Schumaker <Anna.Schumaker@netapp.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>