Enforce SINGLE_NODE_SINGLE_WRITER access mode in NodePublishVolume

[chrishenzie]

What type of PR is this?
/kind feature

What this PR does / why we need it:
This is a first draft of adding support for SINGLE_NODE_SINGLE_WRITER access mode enforcement in the hostpath driver.

See the second table in this section for more details:
https://github.com/container-storage-interface/spec/blob/v1.7.0/spec.md#nodepublishvolume

NOTE: This is hacky. Any suggestions for improvement are much appreciated.

Which issue(s) this PR fixes:
Fixes #380

Does this PR introduce a user-facing change?:

Enforces volumes the with SINGLE_NODE_SINGLE_WRITER access mode can only be mounted at one target path at a time

Testing:
This was tested using the k8s e2e.test binary to install the (custom) hostpath driver and run pods on the same host.

make WHAT=test/e2e/e2e.test

_output/local/bin/linux/amd64/e2e.test \
  --kubeconfig="${HOME}/.kube/config" \
  -ginkgo.focus='csi-hostpath.*should block a second pod from using an in-use ReadWriteOncePod volume on the same node'

/sig storage
/cc @msau42
/cc @jsafrane

[chrishenzie]

/retest

Failed due to:

{"msg":"PASSED External Storage [Driver: hostpath.csi.k8s.io] [Testpattern: Generic Ephemeral-volume (default fs) (immediate-binding)] ephemeral should create read-only inline ephemeral volume","total":-1,"completed":1,"skipped":279,"failed":1,"failures":["External Storage [Driver: hostpath.csi.k8s.io] [Testpattern: Dynamic PV (default fs)] capacity provides storage capacity information"]}
{"msg":"FAILED External Storage [Driver: hostpath.csi.k8s.io] [Testpattern: Dynamic PV (default fs)] capacity provides storage capacity information","total":-1,"completed":0,"skipped":183,"failed":1,"failures":["External Storage [Driver: hostpath.csi.k8s.io] [Testpattern: Dynamic PV (default fs)] capacity provides storage capacity information"]}

[It] provides storage capacity information
  test/e2e/storage/testsuites/capacity.go:112
[1m[0m: Creating a StorageClass
Dec  7 02:13:55.775: FAIL: Timed out after 60.006s.
after creating storage class
no CSIStorageCapacity objects for storage class "capacity-5029-e2e-sc6xqbw"

[chrishenzie]

Bumping this, is there any other feedback I can address?

[jsafrane]

/lgtm
/approve
sorry about the delay, too much work to do

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chrishenzie, jsafrane

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [jsafrane]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[chrishenzie]

Np, thx for the review!