Remove support for btrfs-progs < 3.12
This merge request was inspired by this comment from Bug 792485 - btrfs check (btrfsck) does not repair
As a side note, btrfsck is an alias of the btrfs check command and is now deprecated.
The oldest supported distributions have these versions of the Linux kernel and btrfs-progs:
Distro EOL kernel btrfs-progs - RHEL / CentOS 7 2024-Jun 3.10.0 4.9.1 - Ubuntu 14.04 LTS 2019-Apr 4.4.0 3.12 - Debian 8 2020-Jun 3.16.0 3.17 - SLES 12 2027-Oct 3.12.28 3.16
Making the oldest supported packages be kernel 3.10 and btrfs-progs 3.12 allows the btrfs support code to be simplied by removing backward compatibility code.