Avoid concurrency errors when combining `/randomizeVcIterations` and `/trackVerificationCoverage` #1481

Job	Run time
Boogie CI (Debug, batch_mode=True)	4m 58s
Boogie CI (Debug, batch_mode=True)	4m 58s
Boogie CI (Debug, batch_mode=False)	5m 26s
Boogie CI (Debug, batch_mode=False)	5m 26s
Boogie CI (Release, batch_mode=True)	6h 0m 14s
Boogie CI (Release, batch_mode=True)	6h 0m 15s
Boogie CI (Release, batch_mode=False)	6m 23s
Boogie CI (Release, batch_mode=False)	6m 23s
	12h 34m 3s

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