run.py: detach shouldn't expect a parameter

--detach is a boolean, shouldn't accept a flag.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
run.py: support daemonize for qemu

Don't use stdio and specify -daemonize when user wants to attach
with qemu.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>