nfsd4: preallocate open stateid in process_open1()

As with the nfs4_file, we'd prefer to find out about any failure before
creating a new file rather than after.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --cc fs/nfsd/nfs4state.c
Simple merge

diff --cc fs/nfsd/xdr4.h
Simple merge