Fix sockaddr_un length calculation

The previous commit 0ab1a26ca767ae36fbbe27b62893670b208fa494
contained a mistake that would break interoperability between
AF_UNIX sockets bound via libcore.io.Posix and (for example)
socket_make_sockaddr_un in socket_local_client.c.

Added a test to confirm the expected sun_path is used and
fixed copyright and toString() in UnixSocketAddress.

Bug: 3106438
Change-Id: I42539a3580abc5ab6445669309e1b1d784cd3bc4
3 files changed