Implement encryptwallet method and test

Author: GideonBature

integration_test/tests/wallet.rs

@@ -153,14 +153,9 @@ fn wallet__dump_wallet() {
 
 #[test]
 fn wallet__encrypt_wallet() {
-    let node = Node::with_wallet(Wallet::None, &[]);
-
-    // NOTE: Create a new wallet and returns a dedicated client instance for it.
-    // This client will send RPCs to the `/wallet/test-wallet` endpoint.
-    let wallet_client = node.create_wallet("test-wallet").expect("createwallet");
+    let node = Node::with_wallet(Wallet::Default, &[]);
 
-    // Use the dedicated client to encrypt the new wallet
-    let _: EncryptWallet = wallet_client.encrypt_wallet("test-passphrase").expect("encryptwallet");
+    let _: EncryptWallet = node.client.encrypt_wallet("test-passphrase").expect("encryptwallet");
 }
 
 #[test]