CLI test: always remove run directory before exiting

[Hypnosphi]

Issue: posttest script runs only when test is successful, so there is run directory left after a CLI test failure. It's a part of workspaces (because we want to use linked packages in smoke tests), so if you run yarn at some point later, this leads to an unintended change in lockfile.

Here I use trap command to intercept EXIT signal and run cleanup command while preserving the exit code

[codecov]

Codecov Report

Merging #2201 into release/3.3 will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           release/3.3    #2201   +/-   ##
============================================
  Coverage        21.98%   21.98%           
============================================
  Files              338      338           
  Lines             6700     6700           
  Branches           890      892    +2     
============================================
  Hits              1473     1473           
  Misses            4556     4556           
  Partials           671      671

Impacted Files	Coverage Δ
app/vue/src/server/config/babel.js	0% <0%> (-100%)	⬇️
app/vue/src/server/utils.js	0% <0%> (-53.58%)	⬇️
lib/components/src/highlight_button.js	0% <0%> (ø)	⬆️
addons/info/src/components/types/ObjectType.js	14.28% <0%> (ø)	⬆️
app/react-native/src/bin/storybook-start.js	0% <0%> (ø)	⬆️
addons/info/src/components/types/proptypes.js	16.66% <0%> (ø)	⬆️
...res__/update-addon-info/update-addon-info.input.js	0% <0%> (ø)	⬆️
addons/info/src/components/types/PrettyPropType.js	10.2% <0%> (ø)	⬆️
addons/knobs/src/components/types/Select.js	7.93% <0%> (ø)	⬆️
addons/info/src/components/types/OneOfType.js	11.11% <0%> (ø)	⬆️
... and 28 more

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