Fix DOGE merged mining: correct RPC port (44555 not 44556)

DOGE testnet4alpha daemon on .27 runs with -rpcport=44555 -port=44556.
The stress test script had the P2P port (44556) as the RPC port, causing
"AuxChainRPC not connected" errors.

Also adds --merged flag to stress test for DOGE testnet4alpha merged
mining support.

Author: frstrtr

stress_test_embedded.sh

@@ -36,4 +36,5 @@ exec "$BINARY" \
     --stratum-min-diff 0.001 \
     --stratum-max-diff 65536 \
     --stratum-target-time 10 \
+    --merged DOGE:2:192.168.86.27:44555:dogecoinrpc:testpass:44556 \
     2>&1 | tee -a "$LOGFILE"