Add back --cert-dir option for kubeadm init phase certs sa

[mattkelly]

What type of PR is this?
/kind bug

What this PR does / why we need it:
This fixes a regression that was introduced that got rid of the --cert-dir option for service account key pair generation. More info available in kubernetes/kubeadm#1354.

Which issue(s) this PR fixes:
Fixes kubernetes/kubeadm#1354

Special notes for your reviewer:
N/A

Does this PR introduce a user-facing change?:

kubeadm: add back `--cert-dir` option for `kubeadm init phase certs sa`

[k8s-ci-robot]

Hi @mattkelly. Thanks for your PR.

I'm waiting for a kubernetes 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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[mattkelly]

/assign @neolit123

[mattkelly]

Testing details:

_output/bin/kubeadm version

kubeadm version: &version.Info{Major:"1", Minor:"14+", GitVersion:"v1.14.0-alpha.1.236+35faaab5708d01", GitCommit:"35faaab5708d01068e8a8e829b8033d81b2313c6", GitTreeState:"clean", BuildDate:"2019-01-24T00:45:23Z", GoVersion:"go1.11.4", Compiler:"gc", Platform:"darwin/amd64"}

_output/bin/kubeadm init phase certs sa -h

Generates the private key for signing service account tokens along with its public key, and saves them into sa.key and sa.pub files. If both files already exist, kubeadm skips the generation step and existing files will be used.

Alpha Disclaimer: this command is currently alpha.

Usage:
  kubeadm init phase certs sa [flags]

Flags:
      --cert-dir string   The path where to save and store the certificates. (default "/etc/kubernetes/pki")
  -h, --help              help for sa

Global Flags:
      --log-file string   If non-empty, use this log file
      --rootfs string     [EXPERIMENTAL] The path to the 'real' host root filesystem.
      --skip-headers      If true, avoid header prefixes in the log messages
  -v, --v Level           log level for V logs

_output/bin/kubeadm init phase certs sa --cert-dir /tmp/pki

[certs] Generating "sa" key and public key

ll /tmp/pki

total 16
-rw-------  1 matt  wheel  1675 Jan 23 19:47 sa.key
-rw-------  1 matt  wheel   451 Jan 23 19:47 sa.pub

[rosti]

Thanks for your contribution @mattkelly !
/lgtm
/priority important-soon
/ok-to-test

[rosti]

@mattkelly one tiny nit, you have double 'd' in Read in the release note.
/assign @fabriziopandini

[neolit123]

thanks @mattkelly
/approve
/hold

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mattkelly, neolit123

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[yagonobre]

Thanks @mattkelly
can you add kubeadm: prefix to release note?

[neolit123]

can you add kubeadm: prefix to release note?

the kubeadm: prefix is nice for the RN, yes.

[mattkelly]

@rosti the word was actually readd as in re-add, but I changed it to add back as I can see why that's confusing :)

@yagonobre @neolit123 I added the kubeadm: prefix to the release note even though I see that comment is crossed off now. If I should remove it again, just let me know.

[neolit123]

/hold cancel
thanks for the update @mattkelly