Add Unit tests

[Sakuralbj]

1.pkg/azuredisk/identityserver and version.
2.pkg/mounter/safe_mounter_unix.

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind test

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #382

Special notes for your reviewer:

Release note:

[k8s-ci-robot]

Hi @Sakuralbj. 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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[andyzhangx]

/ok-to-test

[andyzhangx]

it's better reuse original PR, actually you could use following command to do rebase, and then git push ... --force, don't need to open a new PR:

git rebase -i HEAD~2

[andyzhangx]

/kind test

[andyzhangx]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andyzhangx, Sakuralbj

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