Fix scenarios test runner

The test log wasn't being appended to properly - so it wasn't very
useful if anything other than the last test failed.
Add scenario showing init regression

When we changed the way that package mocking was enabled, we
accidentally broke the running of init functions at the same time.
Add a scenario that depends on working init functions in mocked and
unmocked packages.
Restore calling of init functions

Restore the ability to run init functions in a way that hopefully means
that we won't call any mocked functions when running the init functions.