Fix two effective_balance bugs

* Initialisation bug: initial `effective_balance` be not greater than `MAX_EFFECTIVE_BALANCE`
* Hysteresis bug: do not prevent `effective_balance` to go from `MAX_EFFECTIVE_BALANCE - 1` to `MAX_EFFECTIVE_BALANCE`

specs/core/0_beacon-chain.md

@@ -1603,10 +1603,10 @@ def process_final_updates(state: BeaconState) -> None:
         state.eth1_data_votes = []
     # Update effective balances with hysteresis
     for index, validator in enumerate(state.validator_registry):
-        balance = min(state.balances[index], MAX_EFFECTIVE_BALANCE)
+        balance = state.balances[index]
         HALF_INCREMENT = EFFECTIVE_BALANCE_INCREMENT // 2
         if balance < validator.effective_balance or validator.effective_balance + 3 * HALF_INCREMENT < balance:
-            validator.effective_balance = balance - balance % EFFECTIVE_BALANCE_INCREMENT
+            validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
     # Update start shard
     state.latest_start_shard = (state.latest_start_shard + get_shard_delta(state, current_epoch)) % SHARD_COUNT
     # Set active index root
@@ -1840,7 +1840,7 @@ def process_deposit(state: BeaconState, deposit: Deposit) -> None:
             activation_epoch=FAR_FUTURE_EPOCH,
             exit_epoch=FAR_FUTURE_EPOCH,
             withdrawable_epoch=FAR_FUTURE_EPOCH,
-            effective_balance=amount - amount % EFFECTIVE_BALANCE_INCREMENT
+            effective_balance=min(amount - amount % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
         ))
         state.balances.append(amount)
     else: