consul_serf_coordinate_adjustment_ms metric increases for multiple days, goes back down and repeats

#### Overview of the Issue

We recently discovered a strange behavior where a particular metric `consul_serf_coordinate_adjustment_ms` for our Consul Servers remains high for a number of days, goes back down and repeats. This metric represents how much consul is adjusting each time it updates: [Github Link](https://github.com/hashicorp/serf/blob/7faa1b06262f70780c3c35ac25a4c96d754f06f3/serf/ping_delegate.go#L77-L80).

#### Snapshots of the Graphs for different Consul servers



Is this the normal behavior? Any ideas why the update operation is spread out across multiple days?

Start with the referenced serf/ping_delegate.go lines and the consul_serf_coordinate_adjustment_ms metric, then compare that behavior with the attached graphs from the Consul servers. Done means determining whether the repeated multi-day increase and decrease is expected and documenting the cause or confirming a bug.

Written by the indexing model from the issue text.