Ticket 49436 - double free in COS in some conditions
    
    Bug Description:  virtualattrs and COS have some serious memory
    ownership issues. What was happening is that COS with multiple
    attributes using the same sp_handle would cause a structure
    to be registered twice. During shutdown we would then trigger
    a double free in the process.
    
    Fix Description:  Change the behaviour of sp_handles to use a
    handle *per* attribute we register to guarantee the assocation
    between them.
    
    https://pagure.io/389-ds-base/issue/49436
    
    Author: wibrown
    
    Review by: mreynolds, vashirov (Thanks!)
    
    (cherry pick from commit ee4428a3f5d2d8e37a7107c7dce9d622fc17d41c)