util/hbitmap: update orig_size on truncate

util/hbitmap: update orig_size on truncate

Without this, hbitmap_next_zero and hbitmap_next_dirty_area are broken
after truncate. So, orig_size is broken since it's introduction in
76d570dc495c56bb.

Fixes: 76d570dc495c56bb
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190805120120.23585-1-vsementsov@virtuozzo.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
(cherry picked from commit 4e4de222799634d8159ee7b9303b9e1b45c6be2c)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>