Authentication with Kerberos credentials

[GamerGirlandCo]

What type of PR is this?

/kind feature

What this PR does / why we need it:
This PR implements authentication with a kerberos principal and password when mounting NFS shares.

Which issue(s) this PR fixes:

Fixes #525

Special notes for your reviewer:

• I changed the Dockerfile's base image to debian:stable-slim
  Justification: services cannot be started due to a missing file /lib/lsb/init-functions
• I changed the Dockerfile's entrypoint to a script (entry.sh)
  The script is created in the Dockerfile inline, and you can review it here
  Justification: this is so we can start necessary services (rpcbind and nfs-common) if and only if we're in the controller pod. Otherwise, the nfsplugin binary is invoked with the exact same arguments the pod's nfs container was started with.

Does this PR introduce a user-facing change?:

Added the ability to authenticate with kerberos-protected NFS shares
The following new parameters may be specified when creating or updating a storage class:
- **`authPrincipal`**
  The principal that will be used to authenticate to the share
- **`authPasswordSecret`**
  The secret containing the authentication password
- **`authKrbConf`**
  The secret containing contents of a krb5.conf with information about how to connect to a realm.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: GamerGirlandCo
Once this PR has been reviewed and has the lgtm label, please assign msau42 for approval. For more information see the Code Review Process.

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[k8s-ci-robot]

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• ✅ login: GamerGirlandCo / name: ☙◦ The Tablet ❀ GamerGirlandCo ◦❧ (13221c1, 16b2aa7, 250ff6d, 2a4e0cd, 41ead10, 530c840, 714dfa5, 8a474ca, 8c62980, 903cfea, a6e1f33, ab4a863, ae1b082, afbbd54, c377d73, c466707, c72a7fe, d615d7f, dd80225, ed9596a, f29f24c, f634818, f9351ae)

[k8s-ci-robot]

Hi @GamerGirlandCo. Thanks for your PR.

I'm waiting for a github.com 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

[GamerGirlandCo]

/retest

[GamerGirlandCo]

/retest

[GamerGirlandCo]

/retest

[GamerGirlandCo]

/test pull-csi-driver-nfs-e2e-capz

[GamerGirlandCo]

/retest-required

[k8s-ci-robot]

@GamerGirlandCo: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-csi-driver-nfs-external-e2e	a6e1f33	link	true	/test pull-csi-driver-nfs-external-e2e
pull-csi-driver-nfs-e2e-capz	a6e1f33	link	false	/test pull-csi-driver-nfs-e2e-capz

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository. I understand the commands that are listed here.