remove exit() from testeth where its possible

[winsvega]

exit() appear to be not really safe with the memory stack.

so this issue is to track its removal from the testeth (by replacing with return).

the exit from --singletetst could be replace with return if instead going into every test case testeth would go to a custom test suite when is set.

[pirapira]

Is it possible to tweak TestHelper to detect --singletest option?

[winsvega]

it could be done with test::Options