tests/db_test: close the database when test is finished

Change-Id: I96fedf9181e89e4d68815b04f494a9c2ecc0e057

tests/db/db_test.c

@@ -979,6 +979,7 @@ int main(int argc, char **argv)
 	test_subscr_sqn();
 
 	printf("Done\n");
+	db_close(dbc);
 	return 0;
 }