In hostap mode don't send data frames to nodes which aren't in state ASSOC.

In hostap mode don't send data frames to nodes which aren't in state ASSOC.

Sending data frames to nodes in other states is wrong since the node's
data structure might not be set up properly in such states.
This could explain occasional "key unset for sw crypto" panics observed
with athn(4) hostap interfaces.

Problem reported and fix tested by Mikolaj Kucharski.