### 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

{
    if (request.fHelp || request.params.size() != 0)
        throw std::runtime_error(
            "listwallets\n"
            "Returns a list of currently loaded wallets.\n"
            "For full information on the wallet, use \"getwalletinfo\"\n"
            "\nResult:\n"
            "[                         (json array of strings)\n"
            "  \"walletname\"            (string) the wallet name\n"
            "   ...\n"
            "]\n"
            "\nExamples:\n"
            + HelpExampleCli("listwallets", "")
            + HelpExampleRpc("listwallets", "")
        );
    UniValue obj(UniValue::VARR);
    for (CWalletRef pwallet : vpwallets) {
        if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
            return NullUniValue;
        }
        LOCK(pwallet->cs_wallet);
        obj.push_back(pwallet->GetName());
    }
    return obj;
}
UniValue resendwallettransactions(const JSONRPCRequest& request)