No longer shutdown after encrypting the wallet

Since the database environment is flushed, closed, and reopened during
EncryptWallet, there is no need to shut down the software anymore.

test/functional/wallet_encryption.py

@@ -30,8 +30,7 @@ class WalletEncryptionTest(BitcoinTestFramework):
         assert_equal(len(privkey), 52)
 
         # Encrypt the wallet
-        self.nodes[0].node_encrypt_wallet(passphrase)
-        self.start_node(0)
+        self.nodes[0].encryptwallet(passphrase)
 
         # Test that the wallet is encrypted
         assert_raises_rpc_error(-13, "Please enter the wallet passphrase with walletpassphrase first", self.nodes[0].dumpprivkey, address)