devices: filter /dev/console out of the node list

Fixed getDeviceNodes() so it won't add /dev/console to the device node
list.

This fixes an issue where containers wouldn't start if
/dev/console is a pts (which is the case when running docker inside
docker), because devpts inodes are special and cannot be created with
mknod: attempting to open the result of doing so will return EIO.

Since later libcontainer would attempt to open the file to mount --bind
over it and fail because of the EIO error, the container wouldn't start
if the /dev/console was a pts, which is the case inside a docker
that was started from a pts.

getDeviceNodes() already filters pts so this change is consistent
with the current behavior.

Signed-off-by: Alejandro Ojeda <alex@x3y.org>