Bugfix: RPC/Mining: GBT should return 1 MB sizelimit before segwit activates

Github-Pull: #9619
Rebased-From: 9fc7f0bce9

src/rpc/mining.cpp

@@ -676,8 +676,12 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
         nSigOpLimit /= WITNESS_SCALE_FACTOR;
     }
     result.push_back(Pair("sigoplimit", nSigOpLimit));
+    if (fPreSegWit) {
+        result.push_back(Pair("sizelimit", (int64_t)MAX_BLOCK_BASE_SIZE));
+    } else {
         result.push_back(Pair("sizelimit", (int64_t)MAX_BLOCK_SERIALIZED_SIZE));
         result.push_back(Pair("weightlimit", (int64_t)MAX_BLOCK_WEIGHT));
+    }
     result.push_back(Pair("curtime", pblock->GetBlockTime()));
     result.push_back(Pair("bits", strprintf("%08x", pblock->nBits)));
     result.push_back(Pair("height", (int64_t)(pindexPrev->nHeight+1)));