Fix hash256() imports

Importing util.* results in the wrong version of hash256 being imported

test/functional/dip4-coinbasemerkleroots.py

@@ -6,7 +6,7 @@ from collections import namedtuple
 
 from test_framework.mininode import *
 from test_framework.test_framework import DashTestFramework
-from test_framework.util import *
+from test_framework.util import p2p_port, assert_equal, sync_blocks, set_node_times
 
 '''
 dip4-coinbasemerkleroots.py

test/functional/llmq-is-cl-conflicts.py

@@ -3,11 +3,13 @@
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 import time
+from decimal import Decimal
 
+from test_framework import mininode
 from test_framework.blocktools import get_masternode_payment, create_coinbase, create_block
 from test_framework.mininode import *
 from test_framework.test_framework import DashTestFramework
-from test_framework.util import *
+from test_framework.util import sync_blocks, p2p_port, assert_raises_jsonrpc, set_node_times
 
 '''
 llmq-is-cl-conflicts.py

test/functional/p2p-instantsend.py

@@ -5,7 +5,8 @@
 
 from test_framework.mininode import *
 from test_framework.test_framework import DashTestFramework
-from test_framework.util import *
+from test_framework.util import isolate_node, set_node_times, reconnect_isolated_node, assert_equal, \
+    assert_raises_jsonrpc
 
 '''
 InstantSendTest -- test InstantSend functionality (prevent doublespend for unconfirmed transactions)