CiaB networking problems between testclient and ExampleService

On an R-CORD CiaB, there is an issue with connectivity between the testclient and ExampleService VM after `make pod-test` has successfully completed. If a ping is started, the first ping will go through but the rest are dropped. (reported by @James)

The issue is specific to CiaB, which is not running the Trellis fabric or a vRouter. The CiaB head node is set up as a gateway for the `vsg-access` and `public` networks. It is apparently getting confused because it sees local traffic for both networks on the same interface (`fabric`) and so it sends out ICMP redirects telling vSG and ExampleService VMs to talk to each other directly.

The workaround seems to be to suppress ICMP redirects on the head node. Running the following as root on the head node before `make pod-test` seems to remove the connectivity issue:

echo 0 | tee /proc/sys/net/ipv4/conf/*/send_redirects