-when processing static nat rule, add a mangle table rule, to mark the traffic
from the guest vm when it has associated static nat rule so that traffic gets
routed using the route tabe of the device which has public ip associated
-fix the case where nic_device_id is empty when ip is getting disassociated
resulting in empty deviceid in ips.json
-add utility methods in CsRule, and CsRoute to add 'ip rule' and 'ip route' rules respectivley
-ensure traffic from all public interfaces are connection marked with device number, and restored
for the reverse traffic. use the connection marked number to do device specific routing table lookup
fill the device specific routing table with default route
-component tests for testing multiple public interfaces of VR
