xfs_db: fix octal conversion logic

xfs_db: fix octal conversion logic

Fix the backwards boolean logic here, which results in weird behavior.

# xfs_db -x -c /dev/sda
xfs_db> print fname
fname = "\000\000\000\000\000\000\000\000\000\000\000\000"
xfs_db> write fname "mo\0h5o"
fname = "mo\005o\000\000\000\000\000\000\000\000"
xfs_db> print fname
fname = "mo\005o\000\000\000\000\000\000\000\000"

Notice that we passed in octal-zero, 'h', '5', 'o', but the fs label is
set to octal-5, 'o' because of the incorrect loop logic.  -Wlogical-op
found this one.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>