along with logic

[ci skip]

client: fix use of T.Fatalf() in test goroutine

* fix plugin launcher SetConfig msgpack params

The plugin launcher tool was passing the wrong byte array into
`SetConfig`, resulting in msgpack decoding errors. This was fixed in
a9490506 (#6725) but accidentally reverted in 6aff18dc

 (#6590).
Co-Authored-By: Chris Baker <1675087+cgbaker@users.noreply.github.com>

Fix demo vagrant provision hung when libssl asks for confirmation

acl_endpoint: permission denied for unauthenticated requests

apply `s/requestAuthToken/requestACLToken/g`

Extends the BasicAllocStats test to include a test for Windows
clients, exercising stats via a powershell `raw_exec` job.

Adds `ListLinuxClientNodes` and `ListWindowsClientNodes` utils so that
we can scope tests to run only when Linux or Windows clients are
available. This prevents waiting on timeouts when running a subset of
the tests against a development cluster (vs our nightly test
cluster).

Migrating the Load-balancing guides to Nomad

e2e/cli/command: close after error handling

* Adds a constraint to prevent tests from landing on Windows
* Improve Terraform output for mixed windows/linux clients
* Makes some Windows client config fixes from 0.10.2 testing

tests: deflake TestHTTP_FreshClientAllocMetrics

The provision shell script tries to install libssl1.1 package as dependency of ca-certificates package.

The installing of libssl requires to restart some services, and it asks for confirmation of this.
But there are no interactive session at this stage, so Vagrant provisioning just hungs.

This commit add a `libraries/restart-without-asking boolean true` setting before installing libssl,
so it doesn't ask confirmation anymore and the provisioning works again.

The test asserts that alloc counts get reported accurately in metrics by
inspecting the metrics endpoint directly.  Sadly, the metrics as
collected by `armon/go-metrics` seem to be stateful and may contain info
from other tests.

This means that the test can fail depending on the order of returned
metrics.

Inspecting the metrics output of one failing run, you can see the
duplicate guage entries but for different node_ids:

```
    {
      "Name": "service-name.default-0a3ba4b6-2109-485e-be74-6864228aed3d.client.allocations.terminal",
      "Value": 10,
      "Labels": {
        "datacenter": "dc1",
        "node_class": "none",
        "node_id": "67402bf4-00f3-bd8d-9fa8-f4d1924a892a"
      }
    },
    {
      "Name": "service-name.default-0a3ba4b6-2109-485e-be74-6864228aed3d.client.allocations.terminal",
      "Value": 0,
      "Labels": {
        "datacenter": "dc1",
        "node_class": "none",
        "node_id": "a2945b48-7e66-68e2-c922-49b20dd4e20c"
      }
    },
```

Further tweaks to CircleCI build scripts

This speeds up building and pushing releases

Added redirects and stub-ified the index page

docs: update connect limitations

docs: address more GH-6762 review comments

Incorporate suggestions in https://github.com/hashicorp/nomad/pull/6762#pullrequestreview-321716747

[ci skip]

document docker dangling container reaper

Co-Authored-By: Michael Schurter <mschurter@hashicorp.com>

Skip running backend and UI changes for docs/website updates, as
indicated by branch name.

drivers: always initialize taskHandle.logger

[ci skip]

Looks like the RecoverTask doesn't set taskHandle.logger field causing
a panic when the handle attempts to log (e.g. when Shutdown or Signaling
fails).

If ACL Request is unauthenticated, we should honor the anonymous token.
This PR makes few changes:

* `GetPolicy` endpoints may return policy if anonymous policy allows it,
or return permission denied otherwise.
* `ListPolicies` returns an empty policy list, or one with anonymous
policy if one exists.

Without this PR, the we return an incomprehensible error.

Before:
```
$ curl http://localhost:4646/v1/acl/policy/doesntexist; echo
acl token lookup failed: index error: UUID must be 36 characters
$ curl http://localhost:4646/v1/acl/policies; echo
acl token lookup failed: index error: UUID must be 36 characters
```

After:
```
$ curl http://localhost:4646/v1/acl/policy/doesntexist; echo
Permission denied
$ curl http://localhost:4646/v1/acl/policies; echo
[]
```

cherry-pick: device plugin authoring guide

added the device plugin authoring guide, made minor formatting changes to task driver plugin authoring guide.