remove addresses from node class hash

[tgross]

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: #708
Ref: #4390
Ref: #19969

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[tgross]

I'm not actually sure there actually are values that fall into this case (the unique attributes from fingerprinting would be attr.unique), but it was one of the test cases.

[tgross]

FWIW it's not entirely clear to me that the computed class hash is a useful optimization as it's currently designed -- most clusters aren't going to have uniform-enough machines around items like CPU models. Maybe we'd get more mileage out of this feature if it were based on an allowlist of attributes instead of "all attributes except ones specifically marked unique". But that's more of a design improvement than this bugfix.