Add inodes to /metrics endpoint

[micahhausler]

Closes #1413

[k8s-bot]

Can one of the admins verify that this patch is reasonable to test? If so, please reply "ok to test".
(Note: "add to whitelist" is no longer supported. Please update configurations in kubernetes/test-infra/jenkins/job-configs/kubernetes-jenkins-pull instead.)

This message will repeat several times in short succession due to jenkinsci/ghprb-plugin#292. Sorry.

[micahhausler]

Can someone "ok to test" this?

[timstclair]

ok to test

[timstclair]

Could you set a non-zero-valued inodes free/total in the test container info?

[k8s-bot]

Jenkins GCE e2e

Build/test passed for commit 7acd82f.

• Build Log

[micahhausler]

@timothysc Updated

[k8s-bot]

Jenkins GCE e2e

Build/test failed for commit 7ae2384.

• Build Log

[micahhausler]

@timstclair I think that the test container can't get the inodes of the device. Do you want me to do a check for if fs.HasInodes {} or just zero-out the test data?

[timstclair]

I think you just need to manually add the values here: https://github.com/google/cadvisor/blob/master/metrics/prometheus_test.go#L130

[k8s-bot]

Jenkins GCE e2e

Build/test failed for commit dd6cc41.

• Build Log

[k8s-bot]

Jenkins GCE e2e

Build/test passed for commit a9bb292.

• Build Log

[timstclair]

LGTM