### 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

+ HelpExampleRpc("rescanblockchain", "100000, 120000")
            );
    }
    LOCK2(cs_main, pwallet->cs_wallet);
    CBlockIndex *pindexStart = chainActive.Genesis();
    CBlockIndex *pindexStop = nullptr;
    if (!request.params[0].isNull()) {
        pindexStart = chainActive[request.params[0].get_int()];
        if (!pindexStart) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid start_height");
        }
    }
    if (!request.params[1].isNull()) {
        pindexStop = chainActive[request.params[1].get_int()];
        if (!pindexStop) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid stop_height");
        }
        else if (pindexStop->nHeight < pindexStart->nHeight) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "stop_height must be greater then start_height");
        }
    }
    
    if (fPruneMode) {
        CBlockIndex *block = pindexStop ? pindexStop : chainActive.Tip();
        while (block && block->nHeight >= pindexStart->nHeight) {
            if (!(block->nStatus & BLOCK_HAVE_DATA)) {
                throw JSONRPCError(RPC_MISC_ERROR, "Can't rescan beyond pruned data. Use RPC call getblockchaininfo to determine your pruned height.");
            }
            block = block->pprev;
        }