can_open_cached() reads values out of the state structure, meaning that
we need the so_lock to have a correct return value. As a bonus, this
helps clear up some potentially confusing code.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>