interop, examples: use localhost instead of 127.0.0.1

[dfawley]

Made via:

grep -rl 127.0.0.1 | grep -v _test.go | xargs sed -i 's/127.0.0.1/localhost/g'

[easwars]

Made via:

grep -rl 127.0.0.1 | grep -v _test.go | xargs sed -i 's/127.0.0.1/localhost/g'

Why do we not want to do this for tests?

[dfawley]

Current usages in tests all appear to be using it as an address or are unit tests, not to serve on a port or dial.