wallet: Ignore .bak files when listing wallet files

Migration creates backup files in the wallet directory with .bak as the
extension. This pollutes the output of listwalletdir with backup files
that most users should not need to care about.

Author: achow101

src/wallet/db.cpp

@@ -42,7 +42,7 @@ std::vector<fs::path> ListDatabases(const fs::path& wallet_dir)
                 (IsBDBFile(BDBDataFile(it->path())) || IsSQLiteFile(SQLiteDataFile(it->path())))) {
                 // Found a directory which contains wallet.dat btree file, add it as a wallet.
                 paths.emplace_back(path);
-            } else if (it.depth() == 0 && it->symlink_status().type() == fs::file_type::regular && IsBDBFile(it->path())) {
+            } else if (it.depth() == 0 && it->symlink_status().type() == fs::file_type::regular && IsBDBFile(it->path()) && it->path().extension() != ".bak") {
                 if (it->path().filename() == "wallet.dat") {
                     // Found top-level wallet.dat btree file, add top level directory ""
                     // as a wallet.

test/functional/wallet_migration.py

@@ -538,10 +538,14 @@ def test_default_wallet(self):
         assert_equal(info["descriptors"], True)
         assert_equal(info["format"], "sqlite")
 
+        walletdir_list = wallet.listwalletdir()
+
         # Check backup existence and its non-empty wallet filename
-        backup_path = self.nodes[0].wallets_path / f'default_wallet_{curr_time}.legacy.bak'
+        backup_filename = f"default_wallet_{curr_time}.legacy.bak"
+        backup_path = self.nodes[0].wallets_path / backup_filename
         assert backup_path.exists()
         assert_equal(str(backup_path), res['backup_path'])
+        assert {"name": backup_filename} not in walletdir_list["wallets"]
 
     def test_direct_file(self):
         self.log.info("Test migration of a wallet that is not in a wallet directory")