Create federation secret with default consul-gossip-encryption-key secret when global.gossipEncryption.autoGenerate is set to true

[david-yu]

Changes proposed in this PR:

• Check to see whether autoGenerate is set to true and use default secret name and secret key to export out gossipEncryptionKey for consul federation secret. Previously the generated gossip encryption key was not exported when setting autoGenerate to true.

How I've tested this PR:

global:
  name: consul
  datacenter: dc1
  image: hashicorp/consul:1.10.3
  tls: 
    enabled: true
  acls: 
    manageSystemACLs: true
    createReplicationToken: true
  federation: 
    enabled: true
    createFederationSecret: true
  gossipEncryption:
    autoGenerate: true
server:
  replicas: 1
ui:
  enabled: true
  service:
    enabled: true
connectInject:
  enabled: true
controller:
  enabled: true
meshGateway:
  enabled: true

Export out consul-federation secret

kubectl get secret consul-federation -o yaml > consul-federation-secret.yaml

Inspect contents of federation secret

> cat consul-federation-secret.yaml
apiVersion: v1
data:
  caCert: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tCk1JSURRekNDQXVpZ0F3SUJBZ0lVWmdhSGU1MGo1NU1mK0gwZmc5eXRKTnBxQ2Nrd0NnWUlLb1pJemowRUF3SXcKZ1pFeEN6QUpCZ05WQkFZVEFsVlRNUXN3Q1FZRFZRUUlFd0pEUVRFV01CUUdBMVVFQnhNTlUyRnVJRVp5WVc1agphWE5qYnpFYU1CZ0dBMVVFQ1JNUk1UQXhJRk5sWTI5dVpDQlRkSEpsWlhReERqQU1CZ05WQkJFVEJUazBNVEExCk1SY3dGUVlEVlFRS0V3NUlZWE5vYVVOdmNuQWdTVzVqTGpFWU1CWUdBMVVFQXhNUFEyOXVjM1ZzSUVGblpXNTAKSUVOQk1CNFhEVEl4TVRFeE1EQTBORGswTmxvWERUTXhNVEV3T0RBME5UQTBObG93Z1pFeEN6QUpCZ05WQkFZVApBbFZUTVFzd0NRWURWUVFJRXdKRFFURVdNQlFHQTFVRUJ4TU5VMkZ1SUVaeVlXNWphWE5qYnpFYU1CZ0dBMVVFCkNSTVJNVEF4SUZObFkyOXVaQ0JUZEhKbFpYUXhEakFNQmdOVkJCRVRCVGswTVRBMU1SY3dGUVlEVlFRS0V3NUkKWVhOb2FVTnZjbkFnU1c1akxqRVlNQllHQTFVRUF4TVBRMjl1YzNWc0lFRm5aVzUwSUVOQk1Ga3dFd1lIS29aSQp6ajBDQVFZSUtvWkl6ajBEQVFjRFFnQUVkbmk1cUI3dTBxMk40dldBRjVaVTNpeXVTS2JrTWxNV2FObmt3VVNWCmRMZjJ0bHc2VlNNelAyelQ5Smx6WDAxTVBzZnZSaTRrVGxaN1pEM0VNcW93QjZPQ0FSb3dnZ0VXTUE0R0ExVWQKRHdFQi93UUVBd0lCaGpBZEJnTlZIU1VFRmpBVUJnZ3JCZ0VGQlFjREFRWUlLd1lCQlFVSEF3SXdEd1lEVlIwVApBUUgvQkFVd0F3RUIvekJvQmdOVkhRNEVZUVJmTm1RNk16TTZPR1U2WkRrNllUTTZZVFE2TW1FNk1HTTZOekE2Ck5XSTZNMk02TjJZNlpUSTZOamc2T0dJNllUTTZaakE2WVRFNk1UZzZNVE02WTJZNk1HTTZZV1E2WlRVNlpqVTYKTVRjNlpUazZPREU2TlRjNll6RTZNMkU2T1dJd2FnWURWUjBqQkdNd1lZQmZObVE2TXpNNk9HVTZaRGs2WVRNNgpZVFE2TW1FNk1HTTZOekE2TldJNk0yTTZOMlk2WlRJNk5qZzZPR0k2WVRNNlpqQTZZVEU2TVRnNk1UTTZZMlk2Ck1HTTZZV1E2WlRVNlpqVTZNVGM2WlRrNk9ERTZOVGM2WXpFNk0yRTZPV0l3Q2dZSUtvWkl6ajBFQXdJRFNRQXcKUmdJaEFOTkdmNGNCYTkrOXFUSTBjeXF4MHc2T0kwYUFLblEwS3pvSjdCdUl1Q1hYQWlFQXZmN053OVI4clhORwpabVNYazNBSTJwQ1hXWmY4QUt5cGk1Z2VLSHAycjBNPQotLS0tLUVORCBDRVJUSUZJQ0FURS0tLS0tCg==
  caKey: LS0tLS1CRUdJTiBFQyBQUklWQVRFIEtFWS0tLS0tCk1IY0NBUUVFSUtoWExJL1RaYkhkZzRYdXFWTjhYMTdJOU4yVGx4K3NUTGpDWk8zcHA5K3NvQW9HQ0NxR1NNNDkKQXdFSG9VUURRZ0FFZG5pNXFCN3UwcTJONHZXQUY1WlUzaXl1U0tia01sTVdhTm5rd1VTVmRMZjJ0bHc2VlNNegpQMnpUOUpselgwMU1Qc2Z2Umk0a1RsWjdaRDNFTXFvd0J3PT0KLS0tLS1FTkQgRUMgUFJJVkFURSBLRVktLS0tLQo=
  gossipEncryptionKey: eUxlLzdGRTZJU3ZBUi8rTS9BM2NzK2NPR25Bbm1tdDJiNGo5eDZxRmw3az0=
  replicationToken: MjZlMGY0MmYtZTdlMy1jYjBmLTVkNzctNDY4YjNhNTZjMDYy
  serverConfigJSON: eyJwcmltYXJ5X2RhdGFjZW50ZXIiOiJkYzEiLCJwcmltYXJ5X2dhdGV3YXlzIjpbIjM0LjEwNS4xMTAuNzE6NDQzIl19
kind: Secret
metadata:
  creationTimestamp: "2021-11-10T04:51:44Z"
  name: consul-federation
  namespace: consul
  resourceVersion: "16343"
  uid: 2b145443-8361-4dd3-abbb-dfd5cc0c3404
type: Opaque

How I expect reviewers to test this PR:

Manually, I'm not sure how to automate it.

Checklist:

• Tests added
• CHANGELOG entry added

  HashiCorp engineers only, community PRs should not add a changelog entry.
  Entries should use present tense (e.g. Add support for...)

[lkysow]

Looks good. Needs a changelog entry.