repair: factor out sparse inodes from finobt reconstruction

repair: factor out sparse inodes from finobt reconstruction

Phase 5 of xfs_repair recreates the on-disk btrees. The free inode btree
(finobt) contains inode records that contain one or more free inodes.
Sparse inodes are marked as free and therefore sparse inode records can
be incorrectly included in the finobt even when no real free inodes are
available in the record.

Update the finobt in-core record traversal helpers to factor out sparse
inodes and only consider inode records with allocated, free inodes for
finobt insertion.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>