[cloud] Improve ipv6 and EC2 classic support in ec2_group integration tests (#32976)
[cloud] Improve ipv6 and EC2 classic support in ec2_group integration tests (#32976)

* ec2_group: fix ipv6 tests to use an explicit VPC

* otherwise would fail on old AWS accounts supporting EC2-classic

* ec2_group: fix tests to use an explicit VPC

* Only run some tests if there is a default vpc associated with the account

thaim/ansible,thaim/ansible