Changeset 1.403.142.29 introduces a pretty nasty race into the RPC
code. Once we've decoded the RPC reply, it needs to be protected
against being overwritten by any resends.

The following patch achieves this by ensuring that the request is
removed from the list xprt->recv in xprt_complete_rqst(). This again
ensures that xprt_lookup_rqst() will fail to find that request until
we put it back on the list.