memlogd: add test cases
memlogd: add test cases

- check writing to the log does not block
- check the log doesn't expand -- it should be finite
- check that client connections don't buffer arbitrary amounts of
  data if the client is slow

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@docker.com>

linuxkit/linuxkit,JohnnyLeone/linuxkit,linuxkit/linuxkit,furious-luke/linuxkit,yankcrime/linuxkit,JohnnyLeone/linuxkit,justincormack/linuxkit,rn/linuxkit,yankcrime/linuxkit,YuPengZTE/linuxkit,furious-luke/linuxkit,justincormack/linuxkit,justincormack/linuxkit,konstruktoid/linuxkit,rn/linuxkit,konstruktoid/linuxkit,yankcrime/linuxkit,rn/linuxkit,JohnnyLeone/linuxkit,djs55/linuxkit,konstruktoid/linuxkit,djs55/linuxkit,deitch/linuxkit,JohnnyLeone/linuxkit,YuPengZTE/linuxkit,djs55/linuxkit,YuPengZTE/linuxkit,linuxkit/linuxkit,rn/linuxkit,djs55/linuxkit,furious-luke/linuxkit,yankcrime/linuxkit,rn/linuxkit,linuxkit/linuxkit,yankcrime/linuxkit,justincormack/linuxkit,linuxkit/linuxkit,YuPengZTE/linuxkit,furious-luke/linuxkit,yankcrime/linuxkit,justincormack/linuxkit,deitch/linuxkit,konstruktoid/linuxkit,deitch/linuxkit,YuPengZTE/linuxkit,deitch/linuxkit,konstruktoid/linuxkit,furious-luke/linuxkit,justincormack/linuxkit,konstruktoid/linuxkit,djs55/linuxkit,JohnnyLeone/linuxkit,deitch/linuxkit,YuPengZTE/linuxkit