DB/Gameobject: Spawn some missing mailboxes

Spawn Missing Mailboxes in Undercity and Stormwind

* 6 In Undercity (previously only 1 mailbox was spawned in whole of undercity) - 7 in total including the 1 already spawned
* 2 In Stormwind (12 where spawned) - 14 in total including the 12 already spawned