xfs_repair: unconditionally free blockmaps when threads complete

xfs_repair: unconditionally free blockmaps when threads complete

blkmap_free() doesn't actually free the block map unless it's
inordinately large; this keeps us from constantly freeing
and re-allocating blockmaps for each inode, which makes sense.

However, once the threads which have allocated these structures
exit, we should actually free them; they can grow up to 2MB
for each of the data and attr maps, for each thread, and not
be freed through the normal blkmap_free() test.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>