light: fix initialization order
infra: fix potential hang in scheduler

It was a bad idea to call brick_msleep() from brick_thread_should_stop()
since the latter is often called from wait_event_*() which is in
turn often called from the scheduler, potentially leading to
recursive scheduler calls.
net: allow tcp tuning via /proc/sys/mars/tcp_tuning/
net: disable MSG_DONTWAIT
net: find out current tcp send buffer space available
client: implement socket bundling