[caclmgrd][DualToR] Fix a case where vlan address is not network address for DualToR Active-active configuration

[vdahiya12]

This PR fixes sonic-net/sonic-host-services#95 where a corner case is not covered, if vlan address of DUT is not network address.
Basically a src IP is added to the SNAT rule so that only packets originating from ToR with src IP as vlan IP get natted by the rule and change the src IP to LoopBack IP

For multiple vlan IP's only the vlan address coming from configuration is picked as the vlan address and not the network address.

We consider a case where there are multiple vlan IP's are example in such format :

Vlan705                 10.131.113.17/28     up/up         N/A                   N/A
Vlan805                 10.131.111.129/26    up/up         N/A                   N/A

  "VLAN_INTERFACE": {
        "Vlan705|10.131.113.17/28": {},
        "Vlan805|10.131.111.129/26": {},

In such a case we expect iptables rules should be :

target     prot opt source               destination         
SNAT       all  --  10.131.113.17        10.131.113.19        to:10.212.64.1
SNAT       all  --  10.131.111.129       10.131.111.131       to:10.212.64.1

where soc_ip's are such :

10.131.111.131, 10.131.113.19

Before this change the souce IP of the vlan is not correctly picked in the iptables rule