Bug #44530 mtr v2 startup very slow on Windows.

MTR is stuck for about 20 seconds checking for free ports.
The reason is that perl's connect()  takes 1 second on windows
if port is not opened.

This patch fixes the mtr_ping_port implementation on Windows
to use Net::Ping for the port checking with small (0.1sec) timeout.

This patch also removes pointless second call to check_ports_free() 
in case of auto build thread.

mysql-test/lib/mtr_process.pl

@@ -21,6 +21,9 @@
 use strict;
 use Socket;
 use Errno;
+use My::Platform;
+use if IS_WINDOWS, "Net::Ping";
+
 
 sub sleep_until_file_created ($$$);
 sub mtr_ping_port ($);
@@ -30,6 +33,25 @@ sub mtr_ping_port ($) {
 
   mtr_verbose("mtr_ping_port: $port");
 
+  if (IS_WINDOWS)
+  {
+    # Under Windows, connect to a port that is not open is slow
+    # It takes ~1sec. Net::Ping with small timeout is much faster.
+    my $ping = Net::Ping->new();
+    $ping->port_number($port);
+   
+    if ($ping->ping("localhost",0.1))
+    {
+       mtr_verbose("USED");
+	   return 1;
+    }
+    else
+    {
+       mtr_verbose("FREE");
+	   return 0;
+    }
+  }
+  
   my $remote= "localhost";
   my $iaddr=  inet_aton($remote);
   if ( ! $iaddr )

mysql-test/mysql-test-run.pl

@@ -1344,13 +1344,12 @@ sub set_build_thread_ports($) {
   else
   {
     $build_thread = $opt_build_thread + $thread - 1;
-  }
-  $ENV{MTR_BUILD_THREAD}= $build_thread;
-
     if (! check_ports_free($build_thread)) {
       # Some port was not free(which one has already been printed)
       mtr_error("Some port(s) was not free")
     }
+  }
+  $ENV{MTR_BUILD_THREAD}= $build_thread;
 
   # Calculate baseport
   $baseport= $build_thread * 10 + 10000;