generic/422: Do not hardcode space used by files

generic/422: Do not hardcode space used by files

Test generic/422 hardcodes in the output file how much space files it
creates are supposed to take up on disk.  This doesn't work when
additional space is allocated for extended attributes for ACLs or
SELinux labels.

Instead, record the actual space used in generic/422.full, and only
check if the writeback changes the space used.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>