Local files can be made accessible to certain users vs random
ports which can be accessible to anyone on a machine so allow
using unix files as a way to start the eventlet backdoor (so that
user and group permissions common on unix are not lost).
To use this new type of files `socat` is needed (or other way
to interact with telnet over a unix domain socket).
For example (with the path at /tmp/my_special_socket):
socat - UNIX-CONNECT:/tmp/my_special_socket
Depends-On: Ia2385879e09991102f8f305ec41dbb651a4374de
Change-Id: I7f25913168ebe5854f360db3d6310b72a56b2b4d