1. Dropped check for (fd < 0) - there is check after open() in the
test, just two lines upper or so.
2. Combined two test to share common code: they differ only by proc
path to open in a dead process.

travis-ci: success for pstree: rename lookup_create_{item <=> pid} (rev2)
Cc: Tycho Andersen <tycho.andersen@canonical.com>
Acked-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>