Bug 952063 - Trigger FxAccountsIACHelper 'onlogin', 'onloginverified' and 'onlogout' events when required. r=alive

Address Alive review comments
Merge pull request #15463 from ferjm/bug952063.fxa.events

Bug 952063 - Trigger FxAccountsIACHelper 'onlogin', 'onverified' an...