lava-dispatcher: tweaks for supporting docker test action

To allow the lava-dispatcher to run in a docker container and the action
it is running use a container we need to expose a few things to allow
the secondary container to be spun up correctly.

1. Expose /var/run/docker.sock to the lava-dispatcher container so
   containers spun up inside it become sibilings.
2. For udev and things like pyudev to see the current device database we
   need to expose /run/udev

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>