[PATCH] test: use correct path in file system tests

[Stephen Warren]

On 4/21/20 4:41 AM, Heinrich Schuchardt wrote:
> For non-root users mkfs.ext4 and fsck.ext4 are not in the search path at
> least on Debian. Use /sbin/mkfs.ext4 and /sbin/fsck.ext4 instead.

Why not just set $PATH correctly before running the tests? This change
prevents the code from finding mkfs via $PATH, which feels wrong; it
assumes all distros install the tool in the same hard-coded location,
and prevents anyone from temporarily using a customized version for
testing purposes via $PATH. Perhaps the code can find mkfs in $PATH, and
only fall back to a hard-coded location if it's not present in $PATH?