Clean .gitignore

Remove files we don't generate by any of used tools.

Change-Id: Ia9500067ed13a80180ad017efa6b231bdd799284
Use stevedore's make_test_instance

Replace the use of TestManager with make_test_instance
to get an instance of the type of manager expected.
The old TestManger class is deprecated.

Change-Id: I73f3202ac7a1420aaa303d5ea2e741b2fe5673e9
Partial-bug: #1273455
Merge "Use stevedore's make_test_instance"
Merge "Clean .gitignore"