Don't allow immediate deallocations for active validators even if the…

… key shares remain the same

There's an exploit where the prior set improperly mints coins, the new set
occurs (resetting the oracle), and they immediately deallocate 49.9% of their
coins (which is more than enough to achieve profitability).

Now, anyone in set must wait until after the next set completes to perform any
deallocation, enabling time to halt upon improper mints.

substrate/validator-sets/pallet/src/lib.rs

@@ -611,16 +611,8 @@ pub mod pallet {
         }
       }
 
-      // If we're not in-set, or this doesn't decrease our key shares, allow immediate deallocation
-      let active = Self::in_set(network, account);
-      if (!active) || (!decreased_key_shares) {
-        if active {
-          // Since it's being immediately deallocated, decrease TotalAllocatedStake
-          TotalAllocatedStake::<T>::set(
-            network,
-            Some(Amount(TotalAllocatedStake::<T>::get(network).unwrap_or(Amount(0)).0 - amount.0)),
-          );
-        }
+      // If we're not in-set, allow immediate deallocation
+      if !Self::in_set(network, account) {
         Self::deposit_event(Event::AllocationDecreased {
           validator: account,
           network,