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 affect 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>