Integration Tests: Force exit of USE

[h-man2]

Is your feature request related to a problem? Please describe.
When adding integration tests to the test suite so-called .in files are createt that contain commands and expected outputs. To end the tests, an explicit exit command needs to be specified at the end of the .in file. This exit is often left out resulting in a forever running integration tests suite.

Describe the solution you'd like
The intergration test ShellIT should always append an exit-command at the end of the generated command file.

Describe alternatives you've considered
Providing a warning, but this just forces a user to to stuff the testsuite can do.

[h-man2]

While it is easy to add an exit at the end of the test in-files, if not present. A problem exists with tests that provide a invalid USE model, i. e., USE exits by itself.

One solution would be to mark this tests with a comment like #expected exit