added check if anonymous token policy exists

[aahel]

Changes proposed in this PR:

Prevent updating anonymous token if it already exists and is attached to the anonymous token policy

How I've tested this PR:

• setup the deafault partiton and create a non-default partition called my-partition.
• modified the anonymous token policy rule.
• created helm deployment in my-partiton using acl bootstrap token with following policies.

acl = "read"
operator = "read"
agent_prefix "" {
  policy = "read"
}

partition "my-partition" {
  acl = "write"
  mesh = "write"
  peering = "write"
  namespace_prefix "" {
    policy = "write"
  }
  service_prefix "" {
    policy = "write"
  }
}

• server-acl-acl init was successfull and anonymous token policy rule didn't get updated

How I expect reviewers to test this PR:

Checklist:

• Tests added
• CHANGELOG entry added

[Ganeshrockz]

It would be good to add test for the changes in configureAnonymousPolicy function

[Ganeshrockz]

Looks good to me. Deferring the approval to someone with more domain context

[thisisnotashwin]

This is looking good. i think we need to think about the unit-test a little more to ensure we are testing this behavior correctly. Otherwise, i like this.

[thisisnotashwin]

This looks good. I dont think i need to review this again but I think we should update the names of the policy in the test.

[aahel]

@david-yu which versions should we backport this to?

[david-yu]

Added backports, thank you.