fix issue #2606

Added a "docker run" option for sizing /dev/shm which is actually
hardcoded to 64M.

The option is -shm="xxx" where xxx is the size in bytes using k,m,g
notation.

Docker-DCO-1.1-Signed-off-by: Julien Vermillard <jvermillar@sierrawireless.com> (github: jvermillard)