e2fsck: don't flush to device opened in read-only mode

If the e2fsck is called with both the -f and -n options, it will
complete with an exit status of 8 due to an error when trying to flush
the io_channel (which was opened read-only) when built on on Cygwin on
Windows 8.1 and Windows 10.  Apparently Cygwin is unhappy when fsync
is called on a file descriptor opened read-only.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
1 file changed