### 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

case BumpFeeResult::INVALID_PARAMETER:
                throw JSONRPCError(RPC_INVALID_PARAMETER, feeBump.getErrors()[0]);
                break;
            case BumpFeeResult::WALLET_ERROR:
                throw JSONRPCError(RPC_WALLET_ERROR, feeBump.getErrors()[0]);
                break;
            default:
                throw JSONRPCError(RPC_MISC_ERROR, feeBump.getErrors()[0]);
                break;
        }
    }
    
    if (!feeBump.signTransaction(pwallet)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Can't sign transaction.");
    }
    
    if(!feeBump.commit(pwallet)) {
        throw JSONRPCError(RPC_WALLET_ERROR, feeBump.getErrors()[0]);
    }
    UniValue result(UniValue::VOBJ);
    result.push_back(Pair("txid", feeBump.getBumpedTxId().GetHex()));
    result.push_back(Pair("origfee", ValueFromAmount(feeBump.getOldFee())));
    result.push_back(Pair("fee", ValueFromAmount(feeBump.getNewFee())));
    UniValue errors(UniValue::VARR);
    for (const std::string& err: feeBump.getErrors())
        errors.push_back(err);
    result.push_back(Pair("errors", errors));
    return result;
}
UniValue generate(const JSONRPCRequest& request)