AP MLD: Reset authenticator state machine's ML info
Authenticator state machine ML info was set only when it was created.
However, if the association is tried again, the state machine will
already exist and hence the ML info will not be refreshed. This leads to
an issue where if in the subsequent association request, the MLD info is
different than the old info, validation of it will fail.
Fix this issue by refreshing the authenticator state machine's ML info
every time association request is handled.