Update labkit to support ttfb_ms
This uses a latest changes merged into labkit that do add ttfb_ms metric into logs.
This will allow us to graph using logs the average response times when using Object Storage or NFS.
- Ref.: labkit!70 (merged)
- Resolves logging part: #479 (closed)
- Does not resolve prometheus metric part: #396
Edited by Kamil Trzciński