### 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

{
    CAmount nFee;
    std::string strSentAccount;
    std::list<COutputEntry> listReceived;
    std::list<COutputEntry> listSent;
    wtx.GetAmounts(listReceived, listSent, nFee, strSentAccount, filter);
    bool fAllAccounts = (strAccount == std::string("*"));
    bool involvesWatchonly = wtx.IsFromMe(ISMINE_WATCH_ONLY);
    
    if ((!listSent.empty() || nFee != 0) && (fAllAccounts || strAccount == strSentAccount))
    {
        for (const COutputEntry& s : listSent)
        {
            UniValue entry(UniValue::VOBJ);
            if (involvesWatchonly || (::IsMine(*pwallet, s.destination) & ISMINE_WATCH_ONLY)) {
                entry.push_back(Pair("involvesWatchonly", true));
            }
            entry.push_back(Pair("account", strSentAccount));
            MaybePushAddress(entry, s.destination);
            entry.push_back(Pair("category", "send"));
            entry.push_back(Pair("amount", ValueFromAmount(-s.amount)));
            if (pwallet->mapAddressBook.count(s.destination)) {
                entry.push_back(Pair("label", pwallet->mapAddressBook[s.destination].name));
            }
            entry.push_back(Pair("vout", s.vout));
            entry.push_back(Pair("fee", ValueFromAmount(-nFee)));
            if (fLong)
                WalletTxToJSON(wtx, entry);
            entry.push_back(Pair("abandoned", wtx.isAbandoned()));
            ret.push_back(entry);