[baseimage]: install ndisc6 package (#3344)

ndisc6 gathers a few diagnostic tools for IPv6 networks including:

 - ndisc6, which performs ICMPv6 Neighbor Discovery in userland,
 - rdisc6, which performs ICMPv6 Router Discovery in userland,
 - rltraceroute6, a UDP/ICMP IPv6 implementation of traceroute,
 - tcptraceroute6, a TCP/IPv6-based traceroute implementation,
 - tcpspray6, a TCP/IP Discard/Echo bandwidth meter,
 - addrinfo, easy script interface for hostname and address resolution,
 - dnssort, DNS sorting script.

Signed-off-by: Guohan Lu <gulv@microsoft.com>

build_debian.sh

@@ -271,7 +271,8 @@ sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y in
     mtr-tiny                \
     locales                 \
     cgroup-tools            \
-    ipmitool
+    ipmitool                \
+    ndisc6
 
 
 if [[ $CONFIGURED_ARCH == amd64 ]]; then