xfs_check: process sparse inode chunks correctly

xfs_check: process sparse inode chunks correctly

Update the inode btree scanning functions to process sparse inode chunks
correctly. For filesystems with sparse inode support enabled, process
each chunk a cluster at a time. Each cluster is checked against the
inobt record to determine if it is a hole and skipped if so.

Note that since xfs_check is deprecated in favor of xfs_repair,  this
adds the minimum support necessary to process sparse inode enabled
filesystems. In other words, this adds no sparse inode specific checks
or verifications. We only update the inobt scanning functions to extend
the existing level of verification to sparse inode enabled filesystems
(e.g., avoid incorrectly tracking sparse regions as inodes). Problems
or corruptions associated with sparse inode records must be detected and
recovered via xfs_repair.

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