NTFS: - Change {__,}ntfs_cluster_free() to also take an optional attribute

        search context as argument.  This allows calling it with the mft
        record mapped.  Update all callers.
      - Fix potential deadlock in ntfs_mft_data_extend_allocation_nolock()
	error handling by passing in the active search context when calling
	ntfs_cluster_free().

Signed-off-by: Anton Altaparmakov <aia21@cantab.net>