Resolve regression leading to 100% CPU utilization on idle

[sgothel]

• Resolves: #9833
• Target version: master

Summary

PR #9916 caused a regression, i.e. leading to 100% CPU utilization on idle, due to WebSocketHandler's checkTimeout not being called and hence no ping sent.

Checklist

• [ ] I have run make prettier-write and formatted the code.
• [ ] All commits have Change-Id
• [ ] I have run tests with make check
• [ ] I have issued make run and manually verified that everything looks okay
• [ ] Documentation (manuals or wiki) has been updated or is not required