[avalanche] Ensure block added to avalanche have the proper acceptance.

Summary:
This ensure the state within avalanche is consistent with the outside world.

Depends on D2142

Test Plan: Adapted test cases.

Reviewers: #bitcoin_abc, Fabien, jasonbcox

Reviewed By: #bitcoin_abc, Fabien, jasonbcox

Subscribers: jasonbcox, teamcity, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D2117