NFS client reuses XID when server returns NFSERR_JUKEBOX

[Chuck Lever]

hi rick-

(your name is in the source file, so i'm asking you first :^)

i have an internal report that FreeBSD 5.3 (and by my examination, 6.0 
too) has a bug around handling an EJUKEBOX from the server.

RFC1813 states that the client should retransmit using a fresh XID if it 
receives NFSERR_JUKEBOX, but i see that the retry logic in 
sys/nfsclient/nfs_socket.c reuses the old XID.

is the fix as easy as generating a new XID in the if {} clause that 
handles the NFSERR_TRYLATER error?