New wait command

[JulienBalestra]

What does this PR do?

This new command remove any logic like:

until curl -sf http://127.0.0.1:8989/ready --connect-timeout 1 -w '\n'
do
    systemctl status pupernetes.service --no-pager --full
    journalctl -u pupernetes.service --no-pager -o cat -n 50 -e

    sleep 10
done

to be used like:

pupernetes wait pupernetes.service

This will nicely tail the associated journald entry without any duplicate.

[pupernetes.service] Starting github.com/DataDog/pupernetes...
[pupernetes.service] I0607 18:05:25.886126   27882 clean.go:32] Removed /home/jb/go/src/github.com/DataDog/pupernetes/sanbox/etcd-data
[pupernetes.service] I0607 18:05:25.886537   27882 clean.go:32] Removed /var/lib/p8s-kubelet
[pupernetes.service] I0607 18:05:25.886567   27882 clean.go:32] Removed /var/log/pods/
[pupernetes.service] I0607 18:05:25.886572   27882 clean.go:163] Cleanup finished
[pupernetes.service] I0607 18:05:25.924006   27882 hostname.go:59] Using hostname: "v1704"
[pupernetes.service] I0607 18:05:26.077163   27882 manifests.go:94] Using template collection of Kubernetes 1.10
[pupernetes.service] I0607 18:05:26.081590   27882 systemd.go:111] Already created systemd unit: p8s-etcd.service, untouched
[pupernetes.service] I0607 18:05:26.081739   27882 systemd.go:111] Already created systemd unit: p8s-kubelet.service, untouched
[pupernetes.service] I0607 18:05:26.082105   27882 systemd.go:111] Already created systemd unit: p8s-kube-apiserver.service, untouched
[pupernetes.service] I0607 18:05:28.600064   27882 setup.go:294] Setup ready /home/jb/go/src/github.com/DataDog/pupernetes/sanbox
[pupernetes.service] I0607 18:05:28.601200   27882 run.go:78] Timeout for this current run is 6h0m0s
[pupernetes.service] I0607 18:05:28.601243   27882 systemd_action.go:41] Starting systemd unit: p8s-etcd.service ...
[pupernetes.service] I0607 18:05:28.607118   27882 systemd_action.go:41] Starting systemd unit: p8s-kubelet.service ...
[pupernetes.service] I0607 18:05:28.611777   27882 systemd_action.go:41] Starting systemd unit: p8s-kube-apiserver.service ...
[pupernetes.service] I0607 18:05:29.614882   27882 state.go:36] Kubenertes apiserver not ready yet: Get http://127.0.0.1:8080/healthz: dial tcp 127.0.0.1:8080: connect: connection refused
[pupernetes.service] I0607 18:05:32.623306   27882 state.go:36] Kubenertes apiserver not ready yet: bad status code for http://127.0.0.1:8080/healthz: 500
[pupernetes.service] I0607 18:05:36.617347   27882 kubectl.go:14] Calling kubectl apply -f /home/jb/go/src/github.com/DataDog/pupernetes/sanbox/manifest-api ...
[pupernetes.service] I0607 18:05:37.597395   27882 kubectl.go:21] Successfully applied manifests:
[pupernetes.service] serviceaccount "coredns" created
[pupernetes.service] clusterrole.rbac.authorization.k8s.io "system:coredns" created
[pupernetes.service] clusterrolebinding.rbac.authorization.k8s.io "system:coredns" created
[pupernetes.service] configmap "coredns" created
[pupernetes.service] deployment.extensions "coredns" created
[pupernetes.service] service "coredns" created
[pupernetes.service] serviceaccount "kube-controller-manager" created
[pupernetes.service] pod "kube-controller-manager" created
[pupernetes.service] daemonset.extensions "kube-proxy" created
[pupernetes.service] daemonset.extensions "kube-scheduler" created
[pupernetes.service] clusterrolebinding.rbac.authorization.k8s.io "p8s-admin" created
[pupernetes.service] I0607 18:05:37.597553   27882 notify.go:39] Compiled with CGO_ENABLED=0, unable to ack the systemd notify. PPID is 1
[pupernetes.service] I0607 18:05:37.597567   27882 run.go:190] Pupernetes is ready
[pupernetes.service] Started github.com/DataDog/pupernetes.
[pupernetes.service] I0607 18:05:38.617325   27882 state.go:66] Kubelet log reports 1 running pods
I0607 18:05:39.207790   27645 wait.go:86] Systemd unit pupernetes.service is running

Motivation

The bash logic produce too much log lines and can saturate the output of the CI.

[xvello]

LGTM!