host: Integrate new logbuf.

Using the same channel for the old logs and the stream, which means I need to
block on Read() in order to have the correct log order, might not be as
efficient.

Signed-off-by: Blaž Hrastnik <blaz.hrast@gmail.com>
WIP

Signed-off-by: Blaž Hrastnik <blaz.hrast@gmail.com>