docker: setup bitcoind docker image in the docker compose yaml file

docker/docker-compose.yml

@@ -15,7 +15,7 @@ services:
         - RPCUSER
         - RPCPASS
         - NETWORK
-        - DEBUG
+        - BTCD_DEBUG
         - MINING_ADDRESS
       entrypoint: ["./start-btcd.sh"]
 
@@ -30,7 +30,8 @@ services:
         - RPCPASS
         - NETWORK
         - CHAIN
-        - DEBUG
+        - LND_DEBUG
+        - BACKEND=btcd
       volumes:
         - shared:/rpc
         - lnd:/root/.lnd