patch 9.0.0323: using common name in tests leads to flaky tests

Problem:    Using common name in tests leads to flaky tests.
Solution:   Rename files and directories to be more specific.
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index 7e18474..a568fb2 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -1492,7 +1492,7 @@
   " Long directory names only work on Unix.
   CheckUnix
 
-  let dirname = getcwd() . "/Xdir"
+  let dirname = getcwd() . "/Xlongdir"
   let longdirname = dirname . repeat('/' . repeat('d', 255), 4)
   try
     call mkdir(longdirname, 'p')
@@ -1729,7 +1729,7 @@
 " Test for editing a directory
 func Test_edit_is_a_directory()
   CheckEnglish
-  let dirname = getcwd() . "/Xdir"
+  let dirname = getcwd() . "/Xeditdir"
   call mkdir(dirname, 'p')
 
   new