AF_UNIX sun_path caps at 107 bytes and node volume directories
(projects/<uuid>/project-files/docker/<uuid>/tmp) exceed it — uBridge
rejects the NIO with 'invalid file path size'. When the wiring path is
too long, create <XDG_RUNTIME_DIR>/gns3/unixio-<node-id> as a symlink
to the real volume directory (same trick as the uBridge control
socket) and reference the alias in the uBridge commands; the symlink is
removed when uBridge stops. Found during E2E with iol-xe:17-18-02.
42e26717e6