This has been backported upstream already
One could also add this to their configuration: ExtraConfig: collectd::plugin::unixsock::deletesocket: true
According to our records, this should be resolved by openstack-tripleo-heat-templates-8.3.1-54.el7ost. This build is available now.
Still not included in 13 -p 2019-08-02.1
f84fe49d1dee 192.168.24.1:8787/rhosp13/openstack-collectd:2019-09-05.1-grades "kolla_start" 12 hours ago Up 12 hours (healthy) collectd