NFSv4.1: fixup use EXCHGID4_FLAG_USE_PNFS_DS for DS server

This patches fixes commit 51d674a5 "NFSv4.1: use
EXCHGID4_FLAG_USE_PNFS_DS for DS server", purpose of that
commit was to mark EXCHANGE_ID to the DS with the appropriate
flag.

However, connection to MDS can return both EXCHGID4_FLAG_USE_PNFS_DS
and EXCHGID4_FLAG_USE_PNFS_MDS set but previous patch would only
remember the USE_PNFS_DS and for the 2nd EXCHANGE_ID send that
to the MDS.

Instead, just mark the pnfs path exclusively.

Fixes: 51d674a5 ("NFSv4.1: use EXCHGID4_FLAG_USE_PNFS_DS for DS server")
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs4proc.c

@@ -8870,8 +8870,6 @@ static int _nfs4_proc_exchange_id(struct nfs_client *clp, const struct cred *cre
 	/* Save the EXCHANGE_ID verifier session trunk tests */
 	memcpy(clp->cl_confirm.data, argp->verifier.data,
 	       sizeof(clp->cl_confirm.data));
-	if (resp->flags & EXCHGID4_FLAG_USE_PNFS_DS)
-		set_bit(NFS_CS_DS, &clp->cl_flags);
 out:
 	trace_nfs4_exchange_id(clp, status);
 	rpc_put_task(task);