o Add b_test_early_cancel_lost100() test to excercise CANCEL received when downstream peer had first 100 trying lost.
o Add b_test_early_cancel_lost100() test to excercise CANCEL received
when downstream peer had first 100 trying lost.

o split base test class so it's possible to alter UA parameters before
any responses are generated and use that to implement
b_test_early_cancel_lost100.

sippy/voiptests,sippy/voiptests