resource/aws_security_group: Fix Missing Id Error
resource/aws_security_group: Fix Missing Id Error

Make security groups more resilient to eventual consistency errors
by adding retries on the existence function in read and update.

See: https://github.com/hashicorp/terraform/issues/6991

Ninir/terraform-provider-aws,nbaztec/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,nbaztec/terraform-provider-aws,nbaztec/terraform-provider-aws,Ninir/terraform-provider-aws,Ninir/terraform-provider-aws,Ninir/terraform-provider-aws,nbaztec/terraform-provider-aws