Please rotate xlogs before snapshotting

Now If You create snapshot tarantool continues using old xlog, so if You create some snapshots inside 50K requests You can receive the following file list:

1.xlog
2.snap
5.snap
10.snap
100.snap
etc

So If a user want to delete history upto 100.snap he will delete 1.xlog file, too. So then if he restart tarantool he will loss his data between 100 and 50000 operations.