[wallet] keypool mark-used and topup

This commit adds basic keypool mark-used and topup:

- try to topup the keypool on initial load
- if a key in the keypool is used, mark all keys before that as used and
try to top up

test/functional/wallet-hd.py

@@ -9,7 +9,6 @@ from test_framework.util import (
     assert_equal,
     connect_nodes_bi,
 )
-import os
 import shutil
 
 
@@ -72,10 +71,12 @@ class WalletHDTest(BitcoinTestFramework):
 
         self.log.info("Restore backup ...")
         self.stop_node(1)
-        os.remove(self.options.tmpdir + "/node1/regtest/wallet.dat")
+        # we need to delete the complete regtest directory
+        # otherwise node1 would auto-recover all funds in flag the keypool keys as used
+        shutil.rmtree(tmpdir + "/node1/regtest/blocks")
+        shutil.rmtree(tmpdir + "/node1/regtest/chainstate")
         shutil.copyfile(tmpdir + "/hd.bak", tmpdir + "/node1/regtest/wallet.dat")
         self.nodes[1] = self.start_node(1, self.options.tmpdir, self.extra_args[1])
-        #connect_nodes_bi(self.nodes, 0, 1)
 
         # Assert that derivation is deterministic
         hd_add_2 = None
@@ -85,11 +86,12 @@ class WalletHDTest(BitcoinTestFramework):
             assert_equal(hd_info_2["hdkeypath"], "m/0'/0'/"+str(_+1)+"'")
             assert_equal(hd_info_2["hdmasterkeyid"], masterkeyid)
         assert_equal(hd_add, hd_add_2)
+        connect_nodes_bi(self.nodes, 0, 1)
+        self.sync_all()
 
         # Needs rescan
         self.stop_node(1)
         self.nodes[1] = self.start_node(1, self.options.tmpdir, self.extra_args[1] + ['-rescan'])
-        #connect_nodes_bi(self.nodes, 0, 1)
         assert_equal(self.nodes[1].getbalance(), num_hd_adds + 1)
 
         # send a tx and make sure its using the internal chain for the changeoutput