journal: ignore invalid journal files

Even if journal files are broken, we can do nothing for recoverying
it. It is better to inform it as log messages and continue the
initialization process.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
journal: clean journal files when sheep exits correctly

Journal files don't have to exist if an owner sheep exits correctly.

Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
call a default signal handler in crash_handler()

This re-raises the signal in the crash handler for the default signal
hanldlers to dump a core file.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
collie: connect to server in collie_exec_req

This simplifies the collie codes a lot.

Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>