test, refactor: add default_wallet_name and wallet_data_filename variables

No changes in behavior

test/functional/wallet_descriptor.py

@@ -24,7 +24,7 @@ class WalletDescriptorTest(BitcoinTestFramework):
         # Make a descriptor wallet
         self.log.info("Making a descriptor wallet")
         self.nodes[0].createwallet(wallet_name="desc1", descriptors=True)
-        self.nodes[0].unloadwallet("")
+        self.nodes[0].unloadwallet(self.default_wallet_name)
 
         # A descriptor wallet should have 100 addresses * 3 types = 300 keys
         self.log.info("Checking wallet info")