bootkube: use host's /etc/hosts entries

Currently, bare metal environment requires resolvable DNS names for API
server and etcd servers. For user without running DNS server locally or
for testing, it would be nice to be able have some workaround for it.
One would be to populate /etc/hosts of nodes with required entries.

This is almost possible, using CLC snippets for controller nodes, except
the bootkube, which runs in rkt container and have it's own /etc/hosts
file, so health check on static kube-apiserver pod never succeeds. To
make it work, rkt parameter --hosts-entry=host needs to be added.

I suggest we add --hosts-entry=host to bootkube, as potential breakage
impact is minimal and this will save as from exposing general
bootkube_rkt_extra_args in the Terraform module/lokocfg.

By the issue, it is not required to be applied on all platforms, but
again, the breakage chance seems minimal and generally we should be
heading towards having quite unified configurations across all the
platforms, so this commit adds it to all of them.

Closes #408

Signed-off-by: Mateusz Gozdek <mateusz@kinvolk.io>

assets/lokomotive-kubernetes/aws/flatcar-linux/kubernetes/cl/controller.yaml.tmpl

@@ -160,6 +160,7 @@ storage:
             --insecure-options=image \
             --net=host \
             --dns=host \
+            --hosts-entry=host \
             --exec=/bootkube -- start --asset-dir=/assets "$@"
     - path: /etc/tmpfiles.d/etcd-wrapper.conf
       filesystem: root

assets/lokomotive-kubernetes/azure/flatcar-linux/kubernetes/cl/controller.yaml.tmpl

@@ -160,6 +160,7 @@ storage:
             --insecure-options=image \
             --net=host \
             --dns=host \
+            --hosts-entry=host \
             --exec=/bootkube -- start --asset-dir=/assets "$@"
 passwd:
   users:

assets/lokomotive-kubernetes/bare-metal/flatcar-linux/kubernetes/cl/controller.yaml.tmpl

@@ -175,6 +175,7 @@ storage:
             --insecure-options=image \
             --net=host \
             --dns=host \
+            --hosts-entry=host \
             --exec=/bootkube -- start --asset-dir=/assets "$@"
     - path: /etc/kubernetes/configure-kubelet-cgroup-driver
       filesystem: root

assets/lokomotive-kubernetes/google-cloud/flatcar-linux/kubernetes/cl/controller.yaml.tmpl

@@ -161,6 +161,7 @@ storage:
             --insecure-options=image \
             --net=host \
             --dns=host \
+            --hosts-entry=host \
             --exec=/bootkube -- start --asset-dir=/assets "$@"
 passwd:
   users:

assets/lokomotive-kubernetes/kvm-libvirt/flatcar-linux/kubernetes/cl/controller.yaml.tmpl

@@ -171,6 +171,7 @@ storage:
             --insecure-options=image \
             --net=host \
             --dns=host \
+            --hosts-entry=host \
             --exec=/bootkube -- start --asset-dir=/assets "$@"
     - path: /etc/kubernetes/configure-kubelet-cgroup-driver
       filesystem: root

assets/lokomotive-kubernetes/packet/flatcar-linux/kubernetes/cl/controller.yaml.tmpl

@@ -210,6 +210,7 @@ storage:
             --insecure-options=image \
             --net=host \
             --dns=host \
+            --hosts-entry=host \
             --exec=/bootkube -- start --asset-dir=/assets "$@"
     - path: /etc/tmpfiles.d/etcd-wrapper.conf
       filesystem: root