batman-adv: protect tt_local_entry from concurrent delete events

batman-adv: protect tt_local_entry from concurrent delete events

The tt_local_entry deletion performed in batadv_tt_local_remove() was neither
protecting against simultaneous deletes nor checking whether the element was
still part of the list before calling hlist_del_rcu().

Replacing the hlist_del_rcu() call with batadv_hash_remove() provides adequate
protection via hash spinlocks as well as an is-element-still-in-hash check to
avoid 'blind' hash removal.

Fixes: 068ee6e204e1 ("batman-adv: roaming handling mechanism redesign")
Reported-by: [email protected]
Signed-off-by: Marek Lindner <[email protected]>
Signed-off-by: Antonio Quartulli <[email protected]>