Collect startup output before logging it

Collect startup output before logging it

We currently do the startup logging in separate chunks. This is
inefficient in terms of network trafic for client/server, and
it also causes output to be potentially mingled together:

<x1> Starting <x1> Starting 1 process1 process

Fix this by logging to a buffer, then transmitting that buffer
in one piece.

Signed-off-by: Jens Axboe <axboe@kernel.dk>