Fix bug #9196 - defer_open is triggered multiple times on the same request.
get_deferred_open_message_state_smb2() is buggy in that it is checking
the wrong things to determine if an open is in the deferred state.
It checks if (smb2req->async == NULL) which is incorrect,
as we're not always async in a deferred open - remove this.
It should check instead state->open_was_deferred as this
is explicity set to 'true' when an open is going deferred,
so add this check.
Signed-off-by: Jeremy Allison <jra@samba.org>