Add change comments in NetworkInterface, InetAddress, MulticastSocket

The classes have all appropriate changes from upstream OpenJDK8u121-b13.

- The change marker for getHardwareAddress was wrong. The upstream
  doesn't cache mac address

Bug: 26238832
Test: m
Change-Id: Ie8084a8ff4f39d9cb2870976daa569d17089d873
3 files changed