Duplicate violations

For the following input, FCV emits four duplicate violations when using the [world readable constraint template](https://github.com/forseti-security/policy-library/blob/master/policies/templates/gcp_storage_bucket_world_readable_v1.yaml). Oddly enough, when adding this same data to the policy-library testcases, duplicate violations are not surfaced. My guess is that the issue is appearing due to the FCV Constraint Framework target rego, the Constraint Framework rego, or the rego rewriter.

```
{
"name": "//storage.googleapis.com/test_all_authenticated_users",
"asset_type": "storage.googleapis.com/Bucket",
"iam_policy": {
"version": 1,
"etag": "BwWKsK1c7h0=",
"bindings": [
{
"role": "roles/storage.legacyBucketOwner",
"members": [
"projectEditor:xyz",
"projectOwner:xyz"
]
},
{
"role": "roles/storage.legacyBucketReader",
"members": [
"projectViewer:xyz"
]
},
{
"role": "roles/storage.objectViewer",
"members": [
"allAuthenticatedUsers"
]
}
]
},
"ancestors": [
"projects/1234",
"folders/1234",
"organizations/12345"
]
}
```