[fix] Makefile fix target 'test' & 'test.sh'

Renamed 'test.sh' to 'test.shell' seems to solve this issue on my ubu204::

    $ make test.sh
    ...
    TEST      robot
    ...
    INSTALL   gecko.driver
    ...
    Running 7 tests
    cat test.sh >test
    cat: test.sh: Datei oder Verzeichnis nicht gefunden
    make: *** [<eingebaut>: test] Fehler 1

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>