### 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

}
    CBlockIndex *stopBlock = pwallet->ScanForWalletTransactions(pindexStart, pindexStop, true);
    if (!stopBlock) {
        if (pwallet->IsAbortingRescan()) {
            throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
        }
        
        stopBlock = pindexStop ? pindexStop : chainActive.Tip();
    }
    else {
        throw JSONRPCError(RPC_MISC_ERROR, "Rescan failed. Potentially corrupted data files.");
    }
    UniValue response(UniValue::VOBJ);
    response.pushKV("start_height", pindexStart->nHeight);
    response.pushKV("stop_height", stopBlock->nHeight);
    return response;
}
extern UniValue abortrescan(const JSONRPCRequest& request); 
extern UniValue dumpprivkey(const JSONRPCRequest& request); 
extern UniValue importprivkey(const JSONRPCRequest& request);
extern UniValue importaddress(const JSONRPCRequest& request);
extern UniValue importpubkey(const JSONRPCRequest& request);
extern UniValue dumpwallet(const JSONRPCRequest& request);
extern UniValue importwallet(const JSONRPCRequest& request);
extern UniValue importprunedfunds(const JSONRPCRequest& request);
extern UniValue removeprunedfunds(const JSONRPCRequest& request);
extern UniValue importmulti(const JSONRPCRequest& request);
extern UniValue rescanblockchain(const JSONRPCRequest& request);
static const CRPCCommand commands[] =
{