nl80211: Delay event processing during command handling

nl80211: Delay event processing during command handling

Unrelated nl80211 events may arrive while the driver is waiting for the
confirmation of another command. These events must not be delivered
immediately as they may confuse the internal state machine. They also
must be delivered, but some commands would cause them to be dropped.

Fix this up by queuing all events for later processing. Note that this
code is not very elegant as libnl does not export the nl_cb_call()
function. Add a hook into the two relevant functions that process
events. This hook will forward command replies to the correct handler
and queue the event if they should not be processed immediately.

Note that in a lot of cases this cannot happen because different nl80211
sockets are used for different purposes. However, the EAPOL frames
specifically have to be delivered over the same socket that all
connection related commands are done. So for these notifications the
race condition can happen and could cause a state confusion in
wpa_supplicant.

An example of this happening was observed in the autogo_pbc test where
wpa_supplicant would initiate a deauth and during that time also handle
an EAPOL frame that itself caused another deauthentication. This
resulted in a double free of wpa_s->current_ssid.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>