hbitmap: fix missing restore count when finish deserialization

The .count of HBitmap is forgot to set in function
hbitmap_deserialize_finish, let's set it to the right value.

Cc: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: Fam Zheng <famz@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: John Snow <jsnow@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Weiping Zhang <zhangweiping@didichuxing.com>
Signed-off-by: Liang Li <liliangleo@didichuxing.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20180118131308.GA2181@liangdeMacBook-Pro.local
Signed-off-by: John Snow <jsnow@redhat.com>