OfTester._test_initialize() expects the transaction id as a return
value of TargetSw.del_test_flow() for checking the error. but this
method at current version does not return the transaction id.
this patch gets del_test_flow() to return the transaction id.
Signed-off-by: Yuichi Ito <ito.yuichi0@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>