Update HAProxy dashboard and alerts

Kolla has switched to using the built in HAProxy metrics source [1].

The new metrics source is not directly compatible, and therefore
we need to update dashboards and alerts relying on the old metrics.

In a few cases, equivalent metrics were not available, so the plots
have been removed.

[1] https://review.opendev.org/c/openstack/kolla-ansible/+/877118

Author: dougszumski