Core/NetworkIO: Removed MSG_VERIFY_CONNECTIVITY as an opcode
Core/Battle.net: Use real account name from account table to auth instead of always constructing bnetId#index. Fixes having to reconfigure addons by players.

*NEW* battle.net only accounts should be created with battlenet_account_id#account_index format in username
Merge branch '4.3.4' of https://github.com/TrinityCore/TrinityCore into 4.3.4