tests: add exit case "KNOWN FAILED"

Now we can mark tests as known to be broken without bothering
users with exit failure. In the build log this "KNOWN FAILED"
may be interpreted as TODO ;)

The main advantage of "known-fail" instead of just skipping
is that we will still find the test diff.

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
tests: allow to add or override test suite options

Now we can do something like this
  make check TS_OPTS="--fake --parallel=32"

Note we still always set --parallel but the last one wins.

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
tests: style Makefile and make output

We break long lines and make output sill looks nice with and without
V=1.

As a side effect we can now run
  make TS_COMMAND="true"
to do nothing but building all check_PROGRAMS.

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>