Fix CohortCharacterizationServiceTest.java tests

[pieterlukasse]

Expected behavior

• unit tests pass

Actual behavior

• unit tests fail with:

  
  Error:    CohortCharacterizationServiceTest.testExportGeneration:105->doTestExportGeneration:132->checkRequest:151 Checking dataitem org.ohdsi.webapi.cohortcharacterization.CohortCharacterizationServiceTest$ParamItem@130c39d9[analysisIds=[107],cohortIds=[2],isSummary=false,isComparative=false] expected:<1> but was:<0>
  Error:    CohortCharacterizationServiceTest.testExportGenerationWithStrata:110->doTestExportGeneration:132->checkRequest:151 Checking dataitem org.ohdsi.webapi.cohortcharacterization.CohortCharacterizationServiceTest$ParamItem@747b18e5[analysisIds=[107],cohortIds=[2],isSummary=false,isComparative=false] expected:<1> but was:<0>

### Steps to reproduce behavior
- run mvn test