Blivet 3.9.2

• tests: Add a simple unit test for listing btrfs subvolumes (vtrefny)
• Fix getting default subvolume ID for mounted btrfs volumes (vtrefny)
• Do not try to get btrfs subvolumes without libblockdev (vtrefny)
• Do not raise not implemented exception when checking if btrfs is empty (vtrefny)
• Try to start stratisd before checking its availability (vtrefny)
• Fix creating Stratis filesystem without size specified (vtrefny)
• Fix printing the partition type UUID (vtrefny)
• Adjust check for btrfs filesystem being empty (vtrefny)
• Fix util.detect_virt on Amazon (vtrefny)
• misc: Vagrantfile update (vtrefny)
• misc: Run pip with --break-system-packages (vtrefny)
• misc: Add missing libmount build dependencies (vtrefny)
• availability: Check for mpath friendly names availability (vtrefny)
• Allow running blivet without libmount Python bindings (vtrefny)
• Fstab cleanup fix (japokorn)
• Fix getting subvolumes for mounted btrfs volumes (vtrefny)