nfsd: Don't unlock the state while it's not locked

In the procedure of CREATE_SESSION, the state is locked after
alloc_conn_from_crses(). If the allocation fails, the function
goes to "out_free_session", and then "out" where there is an
unlock function.

Signed-off-by: Yanchuan Nian <ycnian@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>