ntfs: do not mark the volume clean in sync_fs when errors were recorded

In the Linux kernel, the following vulnerability has been resolved:

ntfs: do not mark the volume clean in sync_fs when errors were recorded

ntfs_put_super() and the remount-read-only path both clear the dirty bit
only when NVolErrors(vol) is false. ntfs_sync_fs() clears it
unconditionally, so any sync() on a volume that recorded an error marks
that volume clean. A volume without this set is then seen as not needing
recovery and it does not run one, so whatever went wrong is never repaired.

This change skips resetting the dirty bit when there are volume errors.

Reproduced on a volume whose $MFTMirr does not match $MFT, which sets the
error flag while leaving the mount read-write: after a write and a sync,
the on-disk volume flags read 0x0000 with this driver and 0x0001 with the
guard in place.