When a node is fingerprinted, we calculate a "computed class" from a hash over a
subset of its fields and attributes. In the scheduler, when a given node fails
feasibility checking (before fit checking) we know that no other node of that
same class will be feasible, and we add the hash to a map so we can reject them
early. This hash cannot include any values that are unique to a given node,
otherwise no other node will have the same hash and we'll never save ourselves
the work of feasibility checking those nodes.
In #4390 we introduce the `nomad.advertise.address` attribute and in #19969 we
introduced `consul.dns.addr` attribute. Both of these are unique per node and
break the hash.
Additionally, we were not correctly filtering attributes out when checking if a
node escaped the class by not filtering for attributes that start with
`unique.`. The test for this introduced in #708 had an inverted assertion, which
allowed this to pass unnoticed since the early days of Nomad.
Ref: https://github.com/hashicorp/nomad/pull/708
Ref: https://github.com/hashicorp/nomad/pull/4390
Ref: https://github.com/hashicorp/nomad/pull/19969
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