[#56345884] setup scripts for integration testing

Added following scripts:
create_walker_ci.rb => creates a vapp from existing vapp_template and
connect vm to default network

configure_walker_ci_vsw.rb => configures the load-balancer, NAT, firewall
rules for walker_ci

Above scripts are one time scripts to configure walker_ci.

switch_power_for_walker_ci.rb => takes power_mode as arguments. powers
on/off the walker_ci vapp. This script will be used to turn on the
walker_ci before running tests. After run, it will turn off the CI.
This is for saving cost