v3.1.1

This fixes a few issues:

• Sets the network_configuration block only when the task network mode was awsvpc
• Allows passing in one or more security group ids viavar.service_security_groups input variable, associating the service with those security groups
• Allows disabling the default egress rule on the security group generated with awsvpc services by setting the var.security_group_default_egress to false.