Make DNS request for plat prefix detection network specific.

When plat prefix detection is done on a non-default network it
must use the network specific version of getaddrinfo() so the
plat prefix corresponds to the particular network.  The network
is specified to clatd via a NetID command line argument.

(cherry picked from commit a1c871c8efad6c0b69e27d3b85e82a27e282b8be)

Change-Id: I270c5afc4b445cf20e95fd3e58eada6bc24b16ef
6 files changed