patch 9.0.0354: MS-Windows: starting a python server for test sometimes fails

Problem:    MS-Windows: starting a python server for test sometimes fails.
Solution:   Increase the waiting time for the port.
diff --git a/src/testdir/shared.vim b/src/testdir/shared.vim
index bb42678..0f0ffe8 100644
--- a/src/testdir/shared.vim
+++ b/src/testdir/shared.vim
@@ -62,8 +62,8 @@
 " Read the port number from the Xportnr file.
 func GetPort()
   let l = []
-  " with 200 it sometimes failed
-  for i in range(400)
+  " with 200 it sometimes failed, with 400 is rarily failed
+  for i in range(600)
     try
       let l = readfile("Xportnr")
     catch