R1:5f3dc3b7aecf

Make storage.mysql-engine.max-size independent on max_allowed_packet

Summary:
I like systems that just work. It is possible to store files larger than max_allowed_packet in MySQL and we shouldn't demand it.

It also fixes a problem when file was smaller than `storage.mysql-engine.max-size` but its escaped version was larger than `max_allowed_packet`.

Test Plan: Reduced the size to 5e4, uploaded 90 kB file, checked the queries in DarkConsole, downloaded the file.

Reviewers: epriestley

Reviewed By…