### 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 (totalAmount > nBalance)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Account has insufficient funds");
    
    CReserveKey keyChange(pwallet);
    CAmount nFeeRequired = 0;
    int nChangePosRet = -1;
    std::string strFailReason;
    bool fCreated = pwallet->CreateTransaction(vecSend, wtx, keyChange, nFeeRequired, nChangePosRet, strFailReason, coin_control);
    if (!fCreated)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, strFailReason);
    CValidationState state;
    if (!pwallet->CommitTransaction(wtx, keyChange, g_connman.get(), state)) {
        strFailReason = strprintf("Transaction commit failed:: %s", state.GetRejectReason());
        throw JSONRPCError(RPC_WALLET_ERROR, strFailReason);
    }
    return wtx.GetHash().GetHex();
}
extern CScript _createmultisig_redeemScript(CWallet * const pwallet, const UniValue& params);
UniValue addmultisigaddress(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() > 3)
    {
        std::string msg = "addmultisigaddress nrequired [\"key\",...] ( \"account\" )\n"
            "\nAdd a nrequired-to-sign multisignature address to the wallet.\n"
            "Each key is a Bitcoin address or hex-encoded public key.\n"
            "If 'account' is specified (DEPRECATED), assign address to that account.\n"