### 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

wtx.strFromAccount = strAccount;
    if (!request.params[4].isNull() && !request.params[4].get_str().empty())
        wtx.mapValue["comment"] = request.params[4].get_str();
    if (!request.params[5].isNull() && !request.params[5].get_str().empty())
        wtx.mapValue["to"]      = request.params[5].get_str();
    EnsureWalletIsUnlocked(pwallet);
    
    CAmount nBalance = pwallet->GetLegacyBalance(ISMINE_SPENDABLE, nMinDepth, &strAccount);
    if (nAmount > nBalance)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Account has insufficient funds");
    CCoinControl no_coin_control; 
    SendMoney(pwallet, dest, nAmount, false, wtx, no_coin_control);
    return wtx.GetHash().GetHex();
}
UniValue sendmany(const JSONRPCRequest& request)
{
    CWallet * const pwallet = GetWalletForJSONRPCRequest(request);
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() < 2 || request.params.size() > 8)
        throw std::runtime_error(
            "sendmany \"fromaccount\" {\"address\":amount,...} ( minconf \"comment\" [\"address\",...] replaceable conf_target \"estimate_mode\")\n"
            "\nSend multiple times. Amounts are double-precision floating point numbers."
            + HelpRequiringPassphrase(pwallet) + "\n"
            "\nArguments:\n"
            "1. \"fromaccount\"         (string, required) DEPRECATED. The account to send the funds from. Should be \"\" for the default account\n"
            "2. \"amounts\"             (string, required) A json object with addresses and amounts\n"
            "    {\n"
            "      \"address\":amount   (numeric or string) The bitcoin address is the key, the numeric amount (can be string) in " + CURRENCY_UNIT + " is the value\n"