nfsd: Fix NFSv4.1/4.2 Claim_Deleg_Cur_FH

When I implemented a test patch using Open Claim_Deleg_Cur_FH
I discovered that the NFSv4.1/4.2 server was broken for this
Open option. Fortunately it is never used by the FreeBSD
client and never used by other clients unless delegations
are enabled. (The FreeBSD NFSv4 server does not have delegations
enabled by default.)

Claim_Deleg_Cur_FH was broken because the code mistakenly
assumed a stateID argument, which is not the case.
This patch fixes the bug by changing the XDR parser to not
expect a stateID and to fill most of the stateID in from the
clientID. The clientID is the first two elements of the "other"
array for the stateID and is sufficient to identify which
client the delegation is issued to. Since there is only one
delegation issued to a client per file, this is sufficient to
locate the correct delegation.

If you are running non-FreeBSD NFSv4.1/4.2 mounts against the
FreeBSD server, you need this patch if you have delegations enabled.

PR: 274574
MFC after: 2 weeks