kudeadm: Replace "master" with "control plane node"

This replaces the word "master" with "control plane node" in order to use
more inclusive language.

Also uses consistent wording / spelling in this context.

References: kubernetes#21621
Suggested-by: Lubomir I. Ivanov <[email protected]>

Author: devurandom

content/en/docs/setup/production-environment/tools/kubeadm/high-availability.md

@@ -36,7 +36,7 @@ LoadBalancer, or with dynamic PersistentVolumes.
 For both methods you need this infrastructure:
 
 - Three machines that meet [kubeadm's minimum requirements](/docs/setup/production-environment/tools/kubeadm/install-kubeadm/#before-you-begin) for
-  the masters
+  the control plane nodes
 - Three machines that meet [kubeadm's minimum
   requirements](/docs/setup/production-environment/tools/kubeadm/install-kubeadm/#before-you-begin) for the workers
 - Full network connectivity between all machines in the cluster (public or
@@ -109,8 +109,8 @@ option. Your cluster requirements may need a different configuration.
     - The `--control-plane-endpoint` flag should be set to the address or DNS and port of the load balancer.
 
     - The `--upload-certs` flag is used to upload the certificates that should be shared
-      across all the control-plane instances to the cluster. If instead, you prefer to copy certs across
-      control-plane nodes manually or using automation tools, please remove this flag and refer to [Manual
+      across all the control plane instances to the cluster. If instead, you prefer to copy certs across
+      control plane nodes manually or using automation tools, please remove this flag and refer to [Manual
       certificate distribution](#manual-certs) section below.
 
     {{< note >}}
@@ -185,7 +185,7 @@ option. Your cluster requirements may need a different configuration.
 ### Steps for the rest of the control plane nodes
 
 {{< note >}}
-Since kubeadm version 1.15 you can join multiple control-plane nodes in parallel.
+Since kubeadm version 1.15 you can join multiple control plane nodes in parallel.
 Prior to this version, you must join new control plane nodes sequentially, only after
 the first node has finished initializing.
 {{< /note >}}
@@ -224,7 +224,7 @@ in the kubeadm config file.
     scp /etc/kubernetes/pki/apiserver-etcd-client.key "${CONTROL_PLANE}":
     ```
 
-    - Replace the value of `CONTROL_PLANE` with the `user@host` of the first control plane machine.
+    - Replace the value of `CONTROL_PLANE` with the `user@host` of the first control plane node.
 
 ### Set up the first control plane node
 
@@ -352,7 +352,7 @@ SSH is required if you want to control all nodes from a single machine.
 
     {{< caution >}}
     Copy only the certificates in the above list. kubeadm will take care of generating the rest of the certificates
-    with the required SANs for the joining control-plane instances. If you copy all the certificates by mistake,
+    with the required SANs for the joining control plane instances. If you copy all the certificates by mistake,
     the creation of additional nodes could fail due to a lack of required SANs.
     {{< /caution >}}