nfsd4: assume test_stateid always has session

Test_stateid is 4.1-only and only allowed after a sequence operation, so
this check is unnecessary.

Cc: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

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