Fix for issue 869

[jonnycornwell]

• JUnit reporter not reporting nested suites and/or tests correctly #869
• Add failing unit test + associated fix

[jsf-clabot]

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[codecov-io]

Codecov Report

Merging #946 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #946   +/-   ##
=======================================
  Coverage   92.45%   92.45%           
=======================================
  Files          58       58           
  Lines        4623     4623           
  Branches     1012     1012           
=======================================
  Hits         4274     4274           
  Misses        349      349

Impacted Files	Coverage Δ
src/lib/reporters/JUnit.ts	97.29% <100%> (ø)	⬆️

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