EcsWebService: Better Fargate support

[dboitnot]

Without a dedicated security group, the Fargate containers get assigned to the VPC's default group. Fargate containers should:

• [x] Be able to join existing security groups
• [ ] Create a dedicated security group
• [ ] Enable remote exec so that we can log into them for troubleshooting.

[dboitnot]

There's support for creating a security group but it doesn't appear to work.