Engine supports the functionality of force remove storage domain, but there is a validation which blocks the remove of the last master storage domain.
The last master storage domain can only be removed by force removing the Data Center.
To support DR site to site with fail back, the engine should have the ability to destroy the last storage domain without removing the Data Center and that way keep the permissions and other properties of the data center unattached.
Remove the validation and add the ability to force remove the last master storage domain
Master storage domain can be forced remove from a Data Center.
Once it is removed the Data Center should change its status to 'uninitialized'