Table "user_ipv6_address" (UserIpv6AddressVO) is empty and seems that…

… it (#3571)

is not used; probably it is a legacy code/table.

Therefore, remove the verification that counts the IPs from
UserIpv6AddressVO in order to check if it can use the network for
deploying new VMs in UI [1].

[1] com.cloud.network.NetworkModelImpl.canUseForDeploy(Network).

server/src/main/java/com/cloud/network/NetworkModelImpl.java

@@ -594,9 +594,6 @@ public boolean canUseForDeploy(Network network) {
             if (!hasFreeIps) {
                 return false;
             }
-            if (network.getIp6Gateway() != null) {
-                hasFreeIps = areThereIPv6AddressAvailableInNetwork(network.getId());
-            }
         } else {
             if (network.getCidr() == null) {
                 s_logger.debug("Network - " + network.getId() +  " has NULL CIDR.");