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_viminfo.vim b/src/testdir/test_viminfo.vim
index 70442ee..c3ec5b0 100644
--- a/src/testdir/test_viminfo.vim
+++ b/src/testdir/test_viminfo.vim
@@ -962,10 +962,10 @@
   call delete('Xviminfo')
 
   " Try to write the viminfo to a directory
-  call mkdir('Xdir')
-  call assert_fails('wviminfo Xdir', 'E137:')
-  call assert_fails('rviminfo Xdir', 'E195:')
-  call delete('Xdir', 'rf')
+  call mkdir('Xvifdir')
+  call assert_fails('wviminfo Xvifdir', 'E137:')
+  call assert_fails('rviminfo Xvifdir', 'E195:')
+  call delete('Xvifdir', 'rf')
 endfunc
 
 " Test for writing to an existing viminfo file merges the file marks