batman-adv: TT_CLIENT_PENDING is never set in struct tt_global_entry

Actually the TT_CLIENT_PENDING flag is never set in the tt_global_entry
structure, therefore this code is useless and can be removed.

Reported-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>