glance charm leaves old entries in haproxy.cfg when adding and removing

I have a requirement to temporarily add an extra unit to a Openstack HA setup, Liberty on Trusty using charms 15.10.

Aside from the fact that there is manual work required to do this, as per LP#1400481, I'm running into an issue when doing the juju add-unit and then juju remove-unit that the haproxy.cfg ends up keeping the removed unit in the backend glance_api section.

This does not occur when I do the same process for cinder.

--- Test Case ---
On juju management server:
$ juju add-unit glance --to lxc:#

... wait a while ..

On unit to be removed:
$ sudo service pacemaker stop ; sudo service corosync stop

On another unit of the service we're working on:
$ sudo crm_node -R <node>

Back on the juju management server:
$ juju remove-unit glance/#

When checking /etc/haproxy/haproxy.cfg on all the units, the entry for the removed glance unit is still present. Juju status of glance shows the expected 3 nodes, but haproxy has 4 entries.

Versions:
$ juju --version
1.25.5-trusty-amd64

$ dpkg-query -W maas
maas 1.9.2+bzr4568-0ubuntu1~trusty1

Glance charm is lp:charms/trusty/glance revno 127.

Please let me know if you need any further information.