Handle 18.04 in APT setup (refs #25462).

3.New_server_deployment/4.APT_upgrade/0_setup.sh

@@ -18,6 +18,8 @@ echo "Updating /etc/apt/sources.list file."
 cp sources16.list /etc/apt/sources.list
 if ( rgrep '14.04' /etc/lsb-release >/dev/null ); then
 	sed -i 's@xenial@trusty@' /etc/apt/sources.list
+elif ( rgrep '18.04' /etc/lsb-release >/dev/null ); then
+	sed -i 's@xenial@bionic@' /etc/apt/sources.list
 fi
 
 # modify sources.list to use ubicast cache