### 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

{
    return pwallet && pwallet->IsCrypted()
        ? "\nRequires wallet passphrase to be set with walletpassphrase call."
        : "";
}
bool EnsureWalletIsAvailable(CWallet * const pwallet, bool avoidException)
{
    if (pwallet) return true;
    if (avoidException) return false;
    if (::vpwallets.empty()) {
        
        
        
        
        
        throw JSONRPCError(
            RPC_METHOD_NOT_FOUND, "Method not found (wallet method is disabled because no wallet is loaded)");
    }
    throw JSONRPCError(RPC_WALLET_NOT_SPECIFIED,
        "Wallet file not specified (must request wallet RPC through /wallet/<filename> uri-path).");
}
void EnsureWalletIsUnlocked(CWallet * const pwallet)
{
    if (pwallet->IsLocked()) {
        throw JSONRPCError(RPC_WALLET_UNLOCK_NEEDED, "Error: Please enter the wallet passphrase with walletpassphrase first.");
    }
}
void WalletTxToJSON(const CWalletTx& wtx, UniValue& entry)