Increase loop.max_loop

Originally created by @intrigeri on #12065 (Redmine)

I’m running an experiment with an arbitrarily large system partition on a (virtual) Tails USB stick. It has all incremental upgrates applied on top of a Tails 2.0 installation. The goal is to identify shortcomings that come with applying many incremental upgrades. It doesn’t boot anymore unless I set loop.max_loop=N, with N large enough, on the kernel command-line. It would be nice if this worked out of the box.

Feature Branch: feature/12065-increase-max-loops