nfsd4: split stateowners into open and lockowners

The stateowner has some fields that only make sense for openowners, and
some that only make sense for lockowners, and I find it a lot clearer if
those are separated out.

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

diff --cc fs/nfsd/nfs4proc.c
Simple merge

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

diff --cc fs/nfsd/nfs4xdr.c
Simple merge

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

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