feat: upgrade kubernetes to 1.18

This PR will pull in the latest release of k8s 1.18 so we can start
validating it through our test suite.

Signed-off-by: Spencer Smith <robertspencersmith@gmail.com>

docs/talosctl/talosctl_cluster_create.md

@@ -27,7 +27,7 @@ talosctl cluster create [flags]
       --initrd-path string          the uncompressed kernel image to use (default "_out/initramfs.xz")
   -i, --input-dir string            location of pre-generated config files
       --install-image string        the installer image to use (default "docker.io/autonomy/installer:latest")
-      --kubernetes-version string   desired kubernetes version to run (default "1.17.3")
+      --kubernetes-version string   desired kubernetes version to run (default "1.18.0")
       --masters int                 the number of masters to create (default 1)
       --memory int                  the limit on memory usage in MB (each container) (default 1024)
       --mtu int                     MTU of the docker bridge network (default 1500)

docs/talosctl/talosctl_gen_config.md

@@ -19,7 +19,7 @@ talosctl gen config <cluster name> https://<load balancer IP or DNS name> [flags
   -h, --help                        help for config
       --install-disk string         the disk to install to (default "/dev/sda")
       --install-image string        the image used to perform an installation (default "docker.io/autonomy/installer:latest")
-      --kubernetes-version string   desired kubernetes version to run (default "1.17.3")
+      --kubernetes-version string   desired kubernetes version to run (default "1.18.0")
   -o, --output-dir string           destination to output generated files
       --registry-mirror strings     list of registry mirrors to use in format: <registry host>=<mirror URL>
       --version string              the desired machine config version to generate (default "v1alpha1")

docs/website/content/v0.3/en/configuration/v1alpha1.md

@@ -35,7 +35,7 @@ machine:
     force: false
 cluster:
   controlPlane:
-    version: 1.17.3
+    version: 1.18.0
     endpoint: https://1.2.3.4
   clusterName: example
   network:

docs/website/content/v0.4/en/configuration/v1alpha1.md

@@ -35,7 +35,7 @@ machine:
     force: false
 cluster:
   controlPlane:
-    version: 1.17.3
+    version: 1.18.0
     endpoint: https://1.2.3.4
   clusterName: example
   network: