scripted-diff: Use wallets_path and chain_path where possible

Instead of passing the datadir and chain name to os.path.join, just use
the existing properties, which are the same.

-BEGIN VERIFY SCRIPT-
 sed -i --regexp-extended 's|\.datadir, self\.chain, .wallets.|.wallets_path|g' $(git grep -l '\.datadir, self\.chain,')
 sed -i --regexp-extended 's|\.datadir, self\.chain,|.chain_path,|g'            $(git grep -l '\.datadir, self\.chain,')
-END VERIFY SCRIPT-

test/functional/tool_wallet.py

@@ -401,7 +401,7 @@ class ToolWalletTest(BitcoinTestFramework):
 
 
     def run_test(self):
-        self.wallet_path = os.path.join(self.nodes[0].datadir, self.chain, 'wallets', self.default_wallet_name, self.wallet_data_filename)
+        self.wallet_path = os.path.join(self.nodes[0].wallets_path, self.default_wallet_name, self.wallet_data_filename)
         self.test_invalid_tool_commands_and_args()
         # Warning: The following tests are order-dependent.
         self.test_tool_wallet_info()