Starting from Queens, Octavia requires jinja2 >= 2.10. The current version of jinja is too told (2.8.x) which breaks things in Octavia side. See bz#1551821
As soon as jinja 2.10 is available (bz#1551821) we will need to adjust the required jinja version by bumping it in the Octavia .spec file.
Update: Both linked RDO patches got merged.
Octavia .spec fix merged and latest published RDO queens and master packages require python2-jinja2 >= 2.10
$ rpm -q --requires python-octavia-2.0.1-0.20180308104615.9f379ae.el7.centos.noarch.rpm | grep jinja
python2-jinja2 >= 2.10