repair: scan and track sparse inode chunks correctly

repair: scan and track sparse inode chunks correctly

Phase 2 of xfs_repair scans the on-disk inobt and creates in-core
records for all inodes in the fs. This also involves marking
free/allocated state of all inodes, internal record verification and
block state management for the inode chunks tracked by inode records.
Various parts of the inobt scan mechanism assume fully allocated inode
records and thus lead to spurious errors when sparse inode records are
encountered.

Update the inobt scan to detect and handle sparse inode records
correctly. Do not set the allocation state of blocks in sparse inode
regions as these blocks do not belong to the record. Do not account
sparse inodes against the ir_freecount as these inodes do not exist and
are not available for allocation by the fs. Finally, track the sparse
status of each individual inode in the in-core inode records for future
reference.

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