patch 9.0.0363: common names in test files causes tests to be flaky

Problem:    Common names in test files causes tests to be flaky.
Solution:   Use more specific names.
diff --git a/src/testdir/test_stat.vim b/src/testdir/test_stat.vim
index de4a204..e801bfc 100644
--- a/src/testdir/test_stat.vim
+++ b/src/testdir/test_stat.vim
@@ -171,7 +171,7 @@
     return
   endif
 
-  silent !ln -s Xfile Xlink
+  silent !ln -s Xlinkfile Xlink
   call assert_equal('link', getftype('Xlink'))
   call delete('Xlink')