fix: prevent losing SSH connection during CNS uninstall - #125

What this PR does / why we need it?

Issue: While uninstalling CNS, system is going unreachable at this step:

TASK [IPTables Cleanup] **************************************************************************************************************************************
changed: [localhost] => (item=iptables -F)
changed: [localhost] => (item=ip link delete cni0)
changed: [localhost] => (item=ip link delete flannel.1)

TASK [Check docker is installed] *****************************************************************************************************************************

After rebooting the machine, everything returns to normal. The issue is that the user has to be physically present at their dev machine whenever it occurs to reboot the system

Reason: IPTables Cleanup task clearing the iptables rules, which can cause the system to become unreachable. As mentioned in this doc, safer approach is to accept all traffic first to avoid ssh lockdown

Changes:
Added new task Reset iptables default policies to ACCEPT before the existing IPTables Cleanup task