This is needed to avoid issues with APs that restart their UPnP,
e.g., when ER reconfigures them. The previously known settings are
now cached and taken into use if an AP is detected to leave
(ssdp:byebye) and then return.
Verify that the UUID given to wps_er_pbc command is known and only
activate PBC mode on the matching AP. The UUID can be that of the
AP or the station/Enrollee.
wps_er_start command now takes an optional parameter that can be used
to configure a filter to only allow UPnP SSDP messages from the
specified IP address. In practice, this limits the WPS ER operations
to a single AP and filters out all other devices in the network.
When starting the protocol run with an Enrollee, clone the AP Settings
and replace the AP MAC Address with the Enrollee MAC Address so that the
correct value is then used in the Credential attribute in M8.
Instead of forcefully deinitializing ER immediately, give it some
time to complete unsubscription and call eloop_terminate() only once
ER code has completed its work.
This avoids some issues in cases where the ER has been started and
stopped multiple times on the same address and an AP may have stored
multiple event notification addresses for the same ER. The random
identifier allows the ER to filter out unexpected messages from further
processing.
