Test: Add a DNS resolver test

This regression test trigger issue #8
"Make Java InetAddress.getHostName() work" by exercising the DNS
resolver on localhost and a dns root server.

The test takes care of specifying NI_NOFQDN to resolve only the
hostname part of localhost ip.

It appears that the DNS ip is not communicated to the libc by
core/dhcp.cci: /etc/resolv.conf is not filled.

Test contributed while waiting for an fix idea to implement.

Signed-off-by: Benoit Canet <benoit@irqsave.net>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>