Fix bug where get_supported_problems_and_mtimes won't recursively scan

[kiritofeng]

Also added a test.

Additional question: should we return a problem multiple times if it has different locations?

[codecov-commenter]

Codecov Report

Base: 81.66% // Head: 84.50% // Increases project coverage by +2.83% 🎉

Coverage data is based on head (26da9de) compared to base (d96b12b).
Patch coverage: 100.00% of modified lines in pull request are covered.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1104      +/-   ##
==========================================
+ Coverage   81.66%   84.50%   +2.83%     
==========================================
  Files         139      139              
  Lines        4995     5000       +5     
==========================================
+ Hits         4079     4225     +146     
+ Misses        916      775     -141     

Impacted Files	Coverage Δ
dmoj/judgeenv.py	68.06% <100.00%> (+5.04%)	⬆️
dmoj/tests/test_globs.py	100.00% <100.00%> (ø)
dmoj/judge.py	54.54% <0.00%> (+1.21%)	⬆️
dmoj/executors/java_executor.py	85.35% <0.00%> (+2.02%)	⬆️
dmoj/cptbox/compiler_isolate.py	55.31% <0.00%> (+6.38%)	⬆️
dmoj/cptbox/tracer.py	76.32% <0.00%> (+15.90%)	⬆️
dmoj/cptbox/handlers.py	100.00% <0.00%> (+26.31%)	⬆️
dmoj/cptbox/isolate.py	89.63% <0.00%> (+38.41%)	⬆️
dmoj/control.py	100.00% <0.00%> (+64.70%)	⬆️

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[Xyene]

Additional question: should we return a problem multiple times if it has different locations?

No, we should return the first one, and maybe print a warning about the second, but not return it.

[Xyene]

LGTM, thanks!