Make sockets blocking by default

Author: msimacek

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/socket/PSocket.java

@@ -110,9 +110,7 @@ private static InetSocketAddress getEphemeralAddress() {
 
     private ServerSocketChannel serverSocket;
 
-    // TODO this should be true by default, but until we have threads, blocking sockets cause too
-    // many deadlocks in the tests
-    private boolean blocking = false;
+    private boolean blocking = true;
 
     private HashMap<Object, Object> options;