### Describe the issue

I added a second new wallet2.dat. Now I wanted to encrypt it, but `bitcoin-cli help` does not show the command to do so, I need to use `bitcoin-cli -rpcwallet=wallet2.dat help`. This is very un-intuitive, and bad for a help function.

### Can you reliably reproduce the issue?

1. have an encrypted default wallet
2. add new multi wallet wallet2.dat via config file or cmd line options
3. naive `bitcoin-cli help` does not show command to encrypt second wallet.

### Expected behaviour

All wallet encryption, lock and unlock commands should be shown unconditionally in `bitcoin-cli help`.

The dynamic hiding of some lines is arguably worse than the benefit with multiple wallets.

### Actual behaviour

`bitcoin-cli help` shows only wallet encryption commands appropriate for the default wallet.

### What version of bitcoin-core are you using?

bitcoind 0.15.0.1~dfsg-1
deb http://ppa.launchpad.net/luke-jr/bitcoin-core-bip148-unofficial-builds/ubuntu zesty main

### Machine specs:
- OS: Debian 9.2

"\nVerify the signature\n"
            + HelpExampleCli("verifymessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\" \"signature\" \"my message\"") +
            "\nAs json rpc\n"
            + HelpExampleRpc("signmessage", "\"1D1ZrZNe3JUo7ZycKEYQQiQAWd9y54F4XX\", \"my message\"")
        );
    LOCK2(cs_main, pwallet->cs_wallet);
    EnsureWalletIsUnlocked(pwallet);
    std::string strAddress = request.params[0].get_str();
    std::string strMessage = request.params[1].get_str();
    CTxDestination dest = DecodeDestination(strAddress);
    if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Invalid address");
    }
    const CKeyID *keyID = boost::get<CKeyID>(&dest);
    if (!keyID) {
        throw JSONRPCError(RPC_TYPE_ERROR, "Address does not refer to key");
    }
    CKey key;
    if (!pwallet->GetKey(*keyID, key)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Private key not available");
    }
    CHashWriter ss(SER_GETHASH, 0);
    ss << strMessageMagic;
    ss << strMessage;
    std::vector<unsigned char> vchSig;
    if (!key.SignCompact(ss.GetHash(), vchSig))
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Sign failed");
    return EncodeBase64(vchSig.data(), vchSig.size());
}
UniValue getreceivedbyaddress(const JSONRPCRequest& request)