feat: connect the socket only if the socket factory created an unconn…

…ected socket

This is useful if the socket factory creates the complete connection,
for example when using Unix sockets.

fixes #587

pgjdbc/src/main/java/org/postgresql/core/PGStream.java

@@ -58,7 +58,9 @@ public PGStream(SocketFactory socketFactory, HostSpec hostSpec, int timeout) thr
     this.hostSpec = hostSpec;
 
     Socket socket = socketFactory.createSocket();
-    socket.connect(new InetSocketAddress(hostSpec.getHost(), hostSpec.getPort()), timeout);
+    if (!socket.isConnected()) {
+      socket.connect(new InetSocketAddress(hostSpec.getHost(), hostSpec.getPort()), timeout);
+    }
     changeSocket(socket);
     setEncoding(Encoding.getJVMEncoding("UTF-8"));