make IPv6 unit test work on systems with eth0

fixes bug 1103074

The link local unit test was failing because it depended on eth0 to
exists.  This mocks getaddrinfo() to ensure a consistent return value
across testing environments.

Change-Id: Ie1a4d837efcacac8c8d2217c164ad751922e1a5f
Merge "make IPv6 unit test work on systems with eth0"