WNM: Keep BTM information until connection completes

WNM: Keep BTM information until connection completes

In the MLD case, the information from the transition management request
is relevant during the association process in order to filter out links
that were disallowed by the BTM request. Also, the information remains
useful should a connection attempt fail.

To enable these scenarios, keep the information around until the
connection has completed. As this might make it impossible to establish
a connection, also clear this information at the same time that a normal
BSS ignore is cleared to avoid getting stuck in case the transition
fails unexpectedly.

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