p2p thread pool for regtest has only 1 thread

pbtc/commands/start.rs

@@ -1,6 +1,6 @@
 use std::net::SocketAddr;
 use sync::create_sync_connection_factory;
-use message::Services;
+use message::{Services, Magic};
 use util::{open_db, init_db, node_table_path};
 use {config, p2p};
 
@@ -10,8 +10,13 @@ pub fn start(cfg: config::Config) -> Result<(), String> {
 	let db = open_db(&cfg);
 	try!(init_db(&cfg, &db));
 
+	let p2p_threads = match cfg.magic {
+		Magic::Regtest => 1,
+		Magic::Testnet | Magic::Mainnet => 4,
+	};
+
 	let p2p_cfg = p2p::Config {
-		threads: 4,
+		threads: p2p_threads,
 		protocol_minimum: 70001,
 		protocol_maximum: 70017,
 		inbound_connections: 10,