Failure to update lists due to timestamp

[say-yawn]

About this Issue

Surfaced from bug 1662895, we noted that a Firefox user who updated to the latest release was experiencing breakages due to their entity list not being updated. The cause was that the Shavar uses timestamp to decide whether an update should happen which means if versioned lists were updated during the same shavar-list-creation script run, the timestamp of the file will be the same resulting in Shavar responding with DO NOT UPDATE even though the content of the file is different.

Acceptance Criteria

• When checking for update needed using /downloads we should check checksum of the file
• Checksum of the file should be everything minus the header
• If the checksum is different, /downloads should respond with the download link for the latest versioned list
• If the checksum is same (regardless of what the version of the list is/was) NO update should happen.