check_keystone_admin gets 404 from /healthcheck on xenial:mitaka

Keystone on xenial:mitaka is missing the endpoint that check_keystone_admin checks for. This endpoint is example.com/healthcheck. This endpoint is enabled through /etc/keystone-paste.ini option by adding:

[filter:healthcheck]
use = egg:oslo.middleware#healthcheck

This is missing from xenial:mitaka, thus this check is invalid and returns a 404.

One possible solution is adding a check to see if keystone version is > mitaka. If so, one possible endpoint to check is just / which gives some info (including a very brief status field).