ACLs filter allocation resource usage on Node API

If filing a bug please include the following:

### Nomad version
Nomad v1.0.0 (cfca6405ad9b5f66dffc8843e3d16f92f3bedb43)

### Operating system and Environment details

Operating system:
- Architecture.......: "x86_64"
- CPU Cores..........: "8"
- Memory.............: "16046" Mb
- OS.................: "Ubuntu"
- Release............: "16.04"
- Kernel.............: "4.4.0-131-generic"

Nomad ACL Enabled.

### Issue

API Call [/v1/node/:node_id/allocations](https://www.nomadproject.io/api-docs/nodes#list-node-allocations) return empty list even allocations presented on node

### Reproduction steps

Simple curl request on node with allocations `curl -v --header "X-Nomad-Token: " "http://:4646/v1/node//allocations"` return empty list

```
< HTTP/1.1 200 OK
< Content-Type: application/json
< Vary: Accept-Encoding
< X-Nomad-Index: 159510
< X-Nomad-Knownleader: true
< X-Nomad-Lastcontact: 0
< Date: Wed, 16 Dec 2020 21:56:13 GMT
< Content-Length: 2
<
[]
```

Second request with index param `curl --header "X-Nomad-Token: " "http://:4646/v1/node//allocations?index=159510"` return empty list after wait about minute.

```
> GET /v1/node//allocations?index=159510 HTTP/1.1
> User-Agent: curl/7.47.0
> Accept: */*
> X-Nomad-Token:
>
< HTTP/1.1 200 OK
< Content-Type: application/json
< Vary: Accept-Encoding
< X-Nomad-Index: 159510
< X-Nomad-Knownleader: true
< X-Nomad-Lastcontact: 0
< Date: Wed, 16 Dec 2020 22:25:44 GMT
< Content-Length: 2
<
[]
```

Token has policies described in docs

Start by reproducing the GET /v1/node/:node_id/allocations request with ACLs enabled and the documented token policy, then compare the result with the allocations shown on that node. Trace the Node API allocation filtering and verify the fix with an ACL-enabled request where authorized allocations are returned rather than an empty list.

Written by the indexing model from the issue text.