rpc: add optional blockhash to waitfornewblock

test/functional/rpc_blockchain.py

@@ -579,7 +579,8 @@ class BlockchainTest(BitcoinTestFramework):
         node.reconsiderblock(rollback_hash)
         # The chain has probably already been restored by the time reconsiderblock returns,
         # but poll anyway.
-        self.wait_until(lambda: node.waitfornewblock(timeout=100)['hash'] == current_hash)
+        self.wait_until(lambda: node.waitfornewblock(current_tip=rollback_header['previousblockhash'])['hash'] == current_hash)
+
         assert_raises_rpc_error(-1, "Negative timeout", node.waitfornewblock, -1)
 
     def _test_waitforblockheight(self):