fixing bug with read replica outputs when no RR is set

Status Job ID Name Coverage
  Test
failed #7229
test

00:00:15

 
Name Stage Failure
failed
test Test There is an unknown failure, please try again
terraform.zip        100% |*******************************| 15859k  0:00:00 ETA

$ unzip /tmp/terraform.zip -d /usr/local/bin
Archive: /tmp/terraform.zip
inflating: terraform
$ terraform validate
Error loading files Error loading /builds/steamhaus/tf_mod_aws_rds/main.tf: Error reading config for output read_replica_rds_instance_id: parse error: syntax error

ERROR: Job failed: exit code 1