Deep nested objects fix (RT Bug #81236)

Wrong packing/unpacking for nested objects

```perl
my $obj = StorableClass->new(
    h => {
         a => [ StorableClass->new(s => 'value'),
         ...
    ],
    ...
} );
my $hashref = $obj->pack;
```

Packs into:
```perl
{
    __CLASS__ => 'StorableClass',
    h => {
        a => [ bless({s => 'value'}, 'StorableClass') ]    # Blessed! XXX
    }
}
```