Redundant and deadlock-prone end listener removal

[gerashegalov]

Related issues
Not yet

Describe the proposed solution
Skip removal of application end listener
a) because it's only called on spark.stop and won't ever be reused
b) because in Spark 2.3.1 it creates a deadlock between stop and onApplicationEnd

Describe alternatives you've considered

• Removing listener after every run
• stopping/recreating spark context beforeEach

Additional context
None

[codecov]

Codecov Report

Merging #52 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #52      +/-   ##
==========================================
- Coverage   84.77%   84.77%   -0.01%     
==========================================
  Files         298      298              
  Lines        9752     9751       -1     
  Branches      353      548     +195     
==========================================
- Hits         8267     8266       -1     
  Misses       1485     1485

Impacted Files	Coverage Δ
...ain/scala/com/salesforce/op/OpWorkflowRunner.scala	86.95% <ø> (-0.12%)	⬇️

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[tovbinm]

How did you discover it? @gerashegalov

[gerashegalov]

@tovbinm I took a thread dump and then looked into solutions.

[tovbinm]

Thank you again @gerashegalov !!