Add metric for persistent volume claims accessmodes.

[Chenditang]

What this PR does / why we need it:
Add metric for persistent volume claims accessmodes.

# HELP kube_persistentvolumeclaim_spec_accessmodes The accessmodes requested by the persistent volume claim.
# TYPE kube_persistentvolumeclaim_spec_accessmodes gauge
kube_persistentvolumeclaim_spec_accessmodes{namespace="default",persistentvolumeclaim="testpvc",accessmodes="ReadWriteOnce"} 0
kube_persistentvolumeclaim_spec_accessmodes{namespace="default",persistentvolumeclaim="testpvc",accessmodes="ReadOnlyMany"} 0
kube_persistentvolumeclaim_spec_accessmodes{namespace="default",persistentvolumeclaim="testpvc",accessmodes="ReadWriteMany"} 1

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #554

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Chenditang
To fully approve this pull request, please assign additional approvers.
We suggest the following additional approver: andyxning

If they are not already assigned, you can assign the PR to them by writing /assign @andyxning in a comment when ready.

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

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

[brancz]

The mode should be a separate metric from the info metric.

[Chenditang]

@brancz PTAL

[brancz]

This lgtm, but we're currently in code freeze until we do the final release of the v1.5.0. Feel free to ping me if I don't come back to this myself once that release is out.

[tariq1890]

I think we've gone way past the code freeze. Can this be rebased? @Chenditang

[brancz]

@tariq1890 you're absolutely right. Thanks for following up. Happy to re-review once rebased.

[fejta-bot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.

If this issue is safe to close now please do so with /close.

Send feedback to sig-testing, kubernetes/test-infra and/or fejta.
/lifecycle stale

[tariq1890]

This PR can be closed since #673 has been merged.

/close

[k8s-ci-robot]

@tariq1890: Closed this PR.

In response to this:

This PR can be closed since #673 has been merged.

/close

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/test-infra repository.