testsuite: remove need_spawn = false support

testsuite: remove need_spawn = false support

Our test suite is a little unique in my experience in that the test can
be either a normal (fork) child or a (re)spawned one. All the other test
frameworks I have used opt for only one of the two.

I'm not entirely sure why we have both since the latter is sufficient for
all use-cases that we have. Perhaps the former was kept as
micro-optimisation?

Currently I am exploring a way to provide the results summary and the
need_spawn = false ones, are printed multiple times. At a glance I
couldn't quite find a way to fix it.

In addition I am also looking at removing/reducing the use of exit()
across the test suite. Where the two code-flows makes that process more
convoluted.

So let's remove one of the code-paths, simplify things and fix the
logging output. If needed we can re-introduce it later on.

NOTE: there's a lot going on here, because clang-format insist on
reformatting bunch of the DEFINE_TEST() instances :-\

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/246
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>