### 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 (request.fHelp || request.params.size() > 3)
        throw std::runtime_error(
            "getbalance ( \"account\" minconf include_watchonly )\n"
            "\nIf account is not specified, returns the server's total available balance.\n"
            "If account is specified (DEPRECATED), returns the balance in the account.\n"
            "Note that the account \"\" is not the same as leaving the parameter out.\n"
            "The server total may be different to the balance in the default \"\" account.\n"
            "\nArguments:\n"
            "1. \"account\"         (string, optional) DEPRECATED. The account string may be given as a\n"
            "                     specific account name to find the balance associated with wallet keys in\n"
            "                     a named account, or as the empty string (\"\") to find the balance\n"
            "                     associated with wallet keys not in any named account, or as \"*\" to find\n"
            "                     the balance associated with all wallet keys regardless of account.\n"
            "                     When this option is specified, it calculates the balance in a different\n"
            "                     way than when it is not specified, and which can count spends twice when\n"
            "                     there are conflicting pending transactions (such as those created by\n"
            "                     the bumpfee command), temporarily resulting in low or even negative\n"
            "                     balances. In general, account balance calculation is not considered\n"
            "                     reliable and has resulted in confusing outcomes, so it is recommended to\n"
            "                     avoid passing this argument.\n"
            "2. minconf           (numeric, optional, default=1) Only include transactions confirmed at least this many times.\n"
            "3. include_watchonly (bool, optional, default=false) Also include balance in watch-only addresses (see 'importaddress')\n"
            "\nResult:\n"
            "amount              (numeric) The total amount in " + CURRENCY_UNIT + " received for this account.\n"
            "\nExamples:\n"
            "\nThe total amount in the wallet with 1 or more confirmations\n"
            + HelpExampleCli("getbalance", "") +
            "\nThe total amount in the wallet at least 6 blocks confirmed\n"
            + HelpExampleCli("getbalance", "\"*\" 6") +
            "\nAs a json rpc call\n"