Download etcd release abort and show error if package not found

[pytimer]

Fixes: #144

Add --fail when using curl download etcd release package.

If etcd release package not found, etcdadm will show below logs:

[root@k8s-1 ~]# etcdadm init --name k8s --release-url http://192.168.10.108/tools/etcd --version 3.3.12 -l debug
INFO[0000] [install] Artifact not found in cache. Trying to fetch from upstream: http://192.168.10.108/tools/etcd
INFO[0000] [install] Downloading & installing etcd http://192.168.10.108/tools/etcd from 3.3.12 to /var/cache/etcdadm/etcd/v3.3.12
INFO[0000] [install] downloading etcd from http://192.168.10.108/tools/etcd/v3.3.12/etcd-v3.3.12-linux-amd64.tar.gz to /var/cache/etcdadm/etcd/v3.3.12/etcd-v3.3.12-linux-amd64.tar.gz

+curl: (22) The requested URL returned error: 404 Not Found
FATA[0000] [install] Unable to fetch artifact from upstream: unable to download etcd: exit status 22

[k8s-ci-robot]

Hi @pytimer. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[dlipovetsky]

/ok-to-test

[chuckha]

/lgtm

Definitely makes sense to fail on 404s. Copying in the man page to show why --fail is good for scripts and the one warning about using it:

       -f, --fail
              (HTTP)  Fail  silently  (no output at all) on server errors. This is mostly done to better enable scripts etc to better deal with failed attempts. In normal cases when an HTTP server fails to deliver a document, it returns an HTML document stating so (which often also describes why and more). This flag will prevent curl from outputting
              that and return error 22.

              This method is not fail-safe and there are occasions where non-successful response codes will slip through, especially when authentication is involved (response codes 401 and 407).

[dlipovetsky]

/approve

Thanks @pytimer for finding and fixing the issue, and @chuckha for the review!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dlipovetsky, pytimer

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