nfsd: Do no try to us idmapd for sec=mariux

When the nfsd module parameter nfs4_disable_idmapping ist set, which is
the default, than a user space idmapd is not required for AUTH_UNIX.

The code used in nfsd to check whether the idmap cache and user space
daemon should be used is

    if (nfs4_disable_idmapping && rqstp->rq_cred.cr_flavor < RPC_AUTH_GSS)

However, we've added our own security flavor AUTH_MARIUX numerically
after AUTH_GSS:

    enum rpc_auth_flavors {
        RPC_AUTH_NULL  = 0,
        RPC_AUTH_UNIX  = 1,
        RPC_AUTH_SHORT = 2,
        RPC_AUTH_DES   = 3,
        RPC_AUTH_KRB   = 4,
        RPC_AUTH_GSS   = 6,
        RPC_AUTH_TLS   = 7,
        RPC_AUTH_MARIUX = 8,
        RPC_AUTH_MAXFLAVOR = 9,
        /* pseudoflavors: */
        RPC_AUTH_GSS_KRB5  = 390003,
        RPC_AUTH_GSS_KRB5I = 390004,
        RPC_AUTH_GSS_KRB5P = 390005,
        RPC_AUTH_GSS_LKEY  = 390006,
        RPC_AUTH_GSS_LKEYI = 390007,
        RPC_AUTH_GSS_LKEYP = 390008,
        RPC_AUTH_GSS_SPKM  = 390009,
        RPC_AUTH_GSS_SPKMI = 390010,
        RPC_AUTH_GSS_SPKMP = 390011,
   };

So the check fails for AUTH_MARIUX. Although it can and should work
with numerical idents from the client, nfsd tries to use idmapd and this
fails for certain operations, because we don't start idmapd in our
environment

Exlicitly allow RPC_AUTH_MARIUX to be used without idmapd.

fs/nfsd/nfs4idmap.c

@@ -619,7 +619,7 @@ numeric_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namel
 static __be32
 do_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namelen, u32 *id)
 {
-	if (nfs4_disable_idmapping && rqstp->rq_cred.cr_flavor < RPC_AUTH_GSS)
+	if (nfs4_disable_idmapping && (rqstp->rq_cred.cr_flavor < RPC_AUTH_GSS || rqstp->rq_cred.cr_flavor == RPC_AUTH_MARIUX))
 		if (numeric_name_to_id(rqstp, type, name, namelen, id))
 			return 0;
 		/*
@@ -632,7 +632,7 @@ do_name_to_id(struct svc_rqst *rqstp, int type, const char *name, u32 namelen, u
 static __be32 encode_name_from_id(struct xdr_stream *xdr,
 				  struct svc_rqst *rqstp, int type, u32 id)
 {
-	if (nfs4_disable_idmapping && rqstp->rq_cred.cr_flavor < RPC_AUTH_GSS)
+	if (nfs4_disable_idmapping && (rqstp->rq_cred.cr_flavor < RPC_AUTH_GSS || rqstp->rq_cred.cr_flavor == RPC_AUTH_MARIUX))
 		return encode_ascii_id(xdr, id);
 	return idmap_id_to_name(xdr, rqstp, type, id);
 }