bug#77887: libparted detects ext4 without journal as ext2

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Package: parted
Version: 3.6
Severity: minor
Tags: patch easy

Reference: <https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1103454>

Dear maintainers,

libparted wrongly detects ext4 without journal as ext2 instead of ext4.
Steps to reproduce:

truncate -s 1G blob
mkfs.ext4 -O ^has_journal blob
blkid blob -> ext4
parted blob print -> ext2
mount -t ext2 blob /mnt -> "couldn't mount as ext2 due to feature 
incompatibilities"
mount -t ext4 blob /mnt -> ok

In libparted/fs/ext2/interface.c, _ext2_generic_probe() considers ext4 
as a subset of ext3 which is ext2 with journal. IMO this is wrong 
because ext4 without journal may have other incompatible features.

Please consider the attached trivial patch (untested).
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