[4.3.4] Achievements/Guilds: Fix guild achievement tracking

This fix achievement tracking, original commit from @DDuarte: https://github.com/TrinityCore/TrinityCore/commit/7ec22c534e8120f2f877e8d31bc3168faccff5ec and send update.

Send update fix the error when you view criteria progress at 0 at login, without this refresh, you need open manually the achievement to view progress value on achievement tracking window.

Thanks to #DDuarte for initial commit and @Kiritoo for send me a sniffs datas.
It doesn't matter in this particular case (because there's 16 bits being written -> 2 bytes) but a call to FlushBits shouldn't be used here. Can you remove it?