Revert "SUNRPC: Fail faster on bad verifier"

This reverts commit 0701214c

.

The premise of this commit was incorrect. There are exactly 2 cases
where rpcauth_checkverf() will return an error:

1) If there was an XDR decode problem (i.e. garbage data).
2) If gss_validate() had a problem verifying the RPCSEC_GSS MIC.

In the second case, there are again 2 subcases:

a) The GSS context expires, in which case gss_validate() will force a
   new context negotiation on retry by invalidating the cred.
b) The sequence number check failed because an RPC call timed out, and
   the client retransmitted the request using a new sequence number,
   as required by RFC2203.

In neither subcase is this a fatal error.

Reported-by: Russell Cattelan <cattelan@thebarn.com>
Fixes: 0701214c

 ("SUNRPC: Fail faster on bad verifier")
Cc: stable@vger.kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>