Test DualStatus

[blegat]

If config.duals is false, we should probably check that DualStatus is NO_SOLUTION. With DeprecatedTests, this isn't really an option since that would isallow solvers that supports duals to run tests without duals.
With the new tests, they can exclude the DualStatus attribute in addition to setting duals to false.
In fact, the docstring might also say that this is a mandatory attribute that should return NO_SOLUTION in case duals are not supported. It's kind of implicit but for a constraint programming solver for instance, it may be unclear that you actually need to implement this:

MathOptInterface.jl/src/attributes.jl

Lines 1663 to 1671 in 98608b8

	DualStatus(result_index::Int = 1)
	A model attribute for the `ResultStatusCode` of the dual result `result_index`.
	If `result_index` is omitted, it defaults to 1.
	See [`ResultCount`](@ref) for information on how the results are ordered.
	If `result_index` is larger than the value of [`ResultCount`](@ref) then
	`NO_SOLUTION` is returned.

See jump-dev/NLopt.jl#169

[odow]

There is default_status_test in modelike.jl. We should run that instead.

We have too many tests that are testing too many things. We need one test per thing.

[blegat]

I guess with the new runtests, NLopt will run this test by default even if duals is false so this resolve the issue.

[odow]

Yes. There are already existing tests for almost every situation. They're just hard for solvers to find and understand if/when they should run them.

Edit: closing in favor of #1398