Automated ban system shouldn't re-create proposals to ban users who were already banned

[taoeffect]

Problem

After a user is automatically banned, if a user who is in the group logs in from a new computer, their client will generate a proposal to ban the user who was already banned:

Solution

Make sure that the logic in 'gi.actions/group/autobanUser' gets run after a complete sync is finished only.

Test using 3 users and http://localhost:3000/app/error-testing to send malformed mutation of type GIErrorIgnoreAndBan.