fix(compatibility-suite): Clean up mock server

[tienvx]

• Fix the root cause described in Compatibility Suite: Random fail on 'Supports a random hexadecimal generator' scenario #687 (comment) for random issue like:
  • Compatibility Suite: Random fail on 'Supports a random hexadecimal generator' scenario #687
  • Compatibility Suite: Random fail on 'Supports a regex generator' scenario #549
  • Compatibility Suite: Random fail on 'Supports using a generator with the request query parameters' scenario #685
• Make mock server's clean up method idempotent

Depends on #686
Tested 150 times.

[coveralls]

Pull Request Test Coverage Report for Build 11429024504

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 96.405%

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Totals
Change from base Build 11397947659:	0.003%
Covered Lines:	2467
Relevant Lines:	2559

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💛 - Coveralls