Fixes leaked lock on error paths; clean up comments

[bowei]

• There were some leaked locks on error paths that didn't make the code review
• Cleaned up some of the code comments to make the semantics more clear.

[google-oss-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bowei, briantkennedy

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](https://github.com/GoogleCloudPlatform/k8s-cloud-provider/blob/master/OWNERS)~~ [bowei] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment