app_manager: Stop checking h.callers in get_handlers()

dynamically registered handlers (vs. ones registered via
set_ev_cls/handler decorators) do not necessarily have h.callers.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
add debian files to make packages for Ubuntu

Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>