* src/df.c (filter_mount_list): Recent commit v8.22-108-g25a2c94
failed to copy file system type along with the updated device name.
Therefore simply replace the existing mount entry with the
current one with all the latest device details. Note the name,
even if not shorter in this entry, will be replaced with a shorter
name in a subsequent mount entry.
* tests/df/skip-duplicates.sh: Add a test case.