batman-adv: fix erroneous client entry duplicate detection

The translation table implementation, namely batadv_compare_tt(),
is used to compare two client entries and deciding if they are the
holding the same information. Each client entry is identified by
its mac address and its VLAN id (VID).
Consequently, batadv_compare_tt() has to not only compare the mac
addresses but also the VIDs.

Without this fix adding a new client entry that possesses the same
mac address as another client but operates on a different VID will
fail because both client entries will considered identical.

Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>