Fixes halo multi-region fail-over regression

Summary:
- After the afr-common.c refactor the quorum accounting broke, this diff
  fixes things so when an alternate brick is swapped in to provide the
  min-replicas quorum accounting works correctly and the FS doesn't go
  RO.  In short, the magic which makes halo clusters seamlessly fail-over
  to a remote region for writes broke :).

Test Plan:
prove -v tests/basic/halo-failover.t ->
https://phabricator.fb.com/P12179467

Reviewers: dph, jackl, cjh

Reviewed By: cjh

Subscribers: meyering

Differential Revision: https://phabricator.fb.com/D1390670

Tasks: 4117827

Change-Id: I2d7fb8ca1e80cd1b21cc12b11b0a3db812321080
Signed-off-by: Kevin Vigor <kvigor>
Reviewed-on: http://review.gluster.org/16203
NetBSD-regression: NetBSD Build System <jenkins.org>
Smoke: Gluster Build System <jenkins.org>
CentOS-regression: Gluster Build System <jenkins.org>
Reviewed-by: Shreyas Siravara <sshreyas>