feat: disable unneeded message-of-the-day sections (#3000)

vhd/packer/install-dependencies.sh

@@ -51,6 +51,8 @@ if [[ ${UBUNTU_RELEASE} == "18.04" ]]; then
   echo "  - ntpstat" >> ${VHD_LOGS_FILEPATH}
 fi
 
+chmod a-x /etc/update-motd.d/??-{motd-news,release-upgrade}
+
 if [[ ${UBUNTU_RELEASE} == "18.04" ]]; then
   overrideNetworkConfig
 fi