connect NLP and revive HS tests

[mlubin]

Ipopt at jump-dev/Ipopt.jl#108 passes the nlp_solver tests except that:

• Direct mode fails because Ipopt doesn't (yet) support names. If I disable names in JuMP then the test passes.
• Automatic mode fails because of UniversalFallback should implement ListOfAttributesSet MathOptInterface.jl#303.

Maybe we don't need to test direct mode here, but it was useful for debugging.

[codecov]

Codecov Report

Merging #1223 into master will decrease coverage by 0.13%.
The diff coverage is 14.28%.

@@            Coverage Diff             @@
##           master    #1223      +/-   ##
==========================================
- Coverage   78.89%   78.75%   -0.14%     
==========================================
  Files          24       24              
  Lines        3406     3413       +7     
==========================================
+ Hits         2687     2688       +1     
- Misses        719      725       +6

Impacted Files	Coverage Δ
src/nlp.jl	78.64% <0%> (-0.66%)	⬇️
src/optimizerinterface.jl	70.58% <50%> (-2.75%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e05b917...3120708. Read the comment docs.