Use COINBASE_MATURITY constant in functional tests.

test/functional/wallet_hd.py

@@ -7,6 +7,7 @@
 import os
 import shutil
 
+from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -48,7 +49,7 @@ class WalletHDTest(BitcoinTestFramework):
 
         # Derive some HD addresses and remember the last
         # Also send funds to each add
-        self.nodes[0].generate(101)
+        self.nodes[0].generate(COINBASE_MATURITY + 1)
         hd_add = None
         NUM_HD_ADDS = 10
         for i in range(1, NUM_HD_ADDS + 1):