Clear connection pools before deleting test database (#2922)

test/Microsoft.Health.Fhir.Shared.Tests.Integration/Persistence/SqlServerFhirStorageTestHelper.cs

@@ -112,6 +112,8 @@ namespace Microsoft.Health.Fhir.Tests.Integration.Persistence
 
         public async Task DeleteDatabase(string databaseName, CancellationToken cancellationToken = default)
         {
+            SqlConnection.ClearAllPools();
+
             await _dbSetupRetryPolicy.ExecuteAsync(async () =>
             {
                 await using SqlConnection connection = await _sqlConnectionBuilder.GetSqlConnectionAsync(_masterDatabaseName, cancellationToken);