Merge pull request #41921 from apprenda/kubeadm_join_ux_update_2

Automatic merge from submit-queue (batch tested with PRs 41921, 41695, 42139, 42090, 41949)

kubeadm: join ux changes

**What this PR does / why we need it**: Update `kubeadm join` UX according to https://github.com/kubernetes/community/pull/381

**Which issue this PR fixes**: fixes # https://github.com/kubernetes/kubeadm/issues/176

**Special notes for your reviewer**: /cc @luxas @jbeda 

**Release note**:
```release-note
NONE
```

hack/verify-flags/known-flags.txt

@@ -154,7 +154,9 @@ disable-attach-detach-reconcile-sync
 disable-filter
 disable-kubenet
 disable-log-dump
+discovery-file
 discovery-port
+discovery-token
 dns-bind-address
 dns-port
 dns-provider
@@ -646,6 +648,7 @@ tcp-services
 terminated-pod-gc-threshold
 test-flags
 test-timeout
+tls-bootstrap-token
 tls-ca-file
 tls-cert-file
 tls-private-key-file
@@ -665,6 +668,8 @@ upgrade-image
 upgrade-target
 use-kubernetes-cluster-service
 use-kubernetes-version
+use-service-account-credentials
+use-taint-based-evictions
 user-whitelist
 use-service-account-credentials
 use-service-account-credentials