Since #11100, in init.cpp `-blockmaxsize` is translated to `-blockmaxweight` with the code:

```
        unsigned int max_size = gArgs.GetArg("-blockmaxsize", 0);
        if (gArgs.SoftSetArg("blockmaxweight", strprintf("%d", max_size * WITNESS_SCALE_FACTOR))) {
```
However SoftSetArg requires the argument to be specified with the leading dash (ie, as `SoftSetArg("-blockmaxweight")`) without the dash the value will not be looked up later (because the later lookups specify it with a dash).

Obvious fix is just to add the dash (`SoftSetArg("-blockmaxweight", ...)`), but if there haven't been any complaints, just removing the option entirely might be better, since current behaviour is the same as if the option is just removed.

I believe this applies to master, 0.16 and 0.15 (due to backport via #11592).

Test case to demonstrate:

```
#!/usr/bin/env python3
"""Test limiting maxblocksize"""

from test_framework.test_framework import BitcoinTestFramework
from test_framework.util import *

class MaxBlockSizeTest(BitcoinTestFramework):
    def set_test_params(self):
        self.num_nodes = 2
        self.extra_args = [["-blockmaxweight=40000"], ["-blockmaxsize=10000"]]

    def run_test(self):
        chain_height = self.nodes[0].getblockcount()
        assert_equal(chain_height, 200)
        self.nodes[0].generate(100)
        self.nodes[1].generate(100)
        self.nodes[0].generate(100) # unspendable

        blk = [None,None]
        for n in [0,1]:
            vsize = 0
            address = self.nodes[n].getnewaddress()
            txes = 0
            while vsize*4 < 84000:
                txid = self.nodes[n].sendtoaddress(address, 0.25)
                tx = self.nodes[n].getrawtransaction(txid, 1)
                vsize += tx["vsize"]
                txes += 1
            self.nodes[n].generate(1)
            blk[n] = self.nodes[n].getblock(self.nodes[n].getbestblockhash())
            self.sync_all()

        assert blk[0]["weight"] <= 40000, "blockmaxweight greater than 40000"
        assert blk[1]["size"] <= 10000 or blk[1]["weight"] <= 40000, "blockmaxsize is greater than 10000"

if __name__ == '__main__':
    MaxBlockSizeTest().main()
```

Cc @jnewbery (who picked this up via an assertion failure in #11862) @TheBlueMatt (who did the original PR)
}
    
    fListen = gArgs.GetBoolArg("-listen", DEFAULT_LISTEN);
    fDiscover = gArgs.GetBoolArg("-discover", true);
    fRelayTxes = !gArgs.GetBoolArg("-blocksonly", DEFAULT_BLOCKSONLY);
    for (const std::string& strAddr : gArgs.GetArgs("-externalip")) {
        CService addrLocal;
        if (Lookup(strAddr.c_str(), addrLocal, GetListenPort(), fNameLookup) && addrLocal.IsValid())
            AddLocal(addrLocal, LOCAL_MANUAL);
        else
            return InitError(ResolveErrMsg("externalip", strAddr));
    }
#if ENABLE_ZMQ
    pzmqNotificationInterface = CZMQNotificationInterface::Create();
    if (pzmqNotificationInterface) {
        RegisterValidationInterface(pzmqNotificationInterface);
    }
#endif
    uint64_t nMaxOutboundLimit = 0; 
    uint64_t nMaxOutboundTimeframe = MAX_UPLOAD_TIMEFRAME;
    if (gArgs.IsArgSet("-maxuploadtarget")) {
        nMaxOutboundLimit = gArgs.GetArg("-maxuploadtarget", DEFAULT_MAX_UPLOAD_TARGET)*1024*1024;
    }
    
    fReindex = gArgs.GetBoolArg("-reindex", false);
    bool fReindexChainState = gArgs.GetBoolArg("-reindex-chainstate", false);
    
    int64_t nTotalCache = (gArgs.GetArg("-dbcache", nDefaultDbCache) << 20);
    nTotalCache = std::max(nTotalCache, nMinDbCache << 20); 
    nTotalCache = std::min(nTotalCache, nMaxDbCache << 20);