It's possible (and still common in some parts) to run
tests that require servo using a desktop servo V2.
In that case, the ServoHost code will create a wholly
unnecessary ssh tunnel to 'localhost'.  Potentially,
that may not even work: ssh to localhost may fail by
requiring a password; it's even possible for a host to
reject connections from the loopback network.

One amusing/infuriating extreme example:  If you have
a desktop servo V3, and manually create your own ssh
tunnel, it works by creating a tunnel to localhost which
then forward to the tunnel on the beaglebone.  Really.
(And yes, I've seen it _work_, but still...)

We should adjust the ServoHost creation code not to
create a tunnel in this case.  The simplest way to do
it is to say "if the servo host is 'localhost', don't
create a tunnel".