Terraform-provider-aws: On plan, redrive_policy is always marked as modified

_This issue was originally opened by @kfrn as hashicorp/terraform#15579. It was migrated here as a result of the provider split. The original body of the issue is below._

Every time I run terraform plan, the redrive policies for my SQS queues show up as modified, even though they actually have no changes.

I'm using a module to create my SQS queues.

resource "aws_sqs_queue" "sqs_queue" {
  name                       = "${var.environment}_${var.name}"
  message_retention_seconds  = "${var.sqs_queue["message_retention_seconds"]}"
  visibility_timeout_seconds = "${var.sqs_queue["visibility_timeout_seconds"]}"

  redrive_policy = <<-JSON
    {
      "deadLetterTargetArn": "${aws_sqs_queue.sqs_dead_queue.arn}",
      "maxReceiveCount": "${var.sqs_queue["max_receive_count"]}"
    }
  JSON
}

resource "aws_sqs_queue" "sqs_dead_queue" {
  name                       = "${var.environment}_${var.name}_dead"
  message_retention_seconds  = "${var.sqs_dead_queue["message_retention_seconds"]}"
  visibility_timeout_seconds = "${var.sqs_dead_queue["visibility_timeout_seconds"]}"
}

maxReceiveCount is set in the module variables:

variable "sqs_queue" {
  type = "map"

  default = {
    message_retention_seconds  = 1209600
    visibility_timeout_seconds = 30
    max_receive_count          = 10
  }
}

Terraform Version

Terraform v0.9.8

Expected Behaviour

That no change is detected for the redrive policies, since no change has been made.

Actual Behaviour

Steps to Reproduce

Please list the steps required to reproduce the issue, for example:

1. terraform get
2. terraform plan -var-file=<var-file>.tfvars -out=<my-update>.plan -state=<current-state-file>.tfstate
3. terraform apply -state-out=<new-state-file>.tfstate <my-update>.plan

References

This problem was discussed in February 2016, here: hashicorp/terraform#5119
It seems to have been because the maxReceiveCount in that person's code was a string, not a number; the bug then garnered a patch (#5888).
So I'm really unsure why this is happening for me. For the record, my maxReceiveCount is definitely an integer.