patch 8.1.1473: new resolve() implementation causes problem for plugins

Problem:    New resolve() implementation causes problem for plugins.
Solution:   Only resolve a resparse point after checking it is needed. (Ken
            Takata, closes #4492)
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index cc1ee8b..a2e4da6 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -276,6 +276,7 @@
   " test for symbolic link to a file
   new Xfile
   wq
+  call assert_equal('Xfile', resolve('Xfile'))
   silent !mklink Xlink Xfile
   if !v:shell_error
     call assert_equal(s:normalize_fname(getcwd() . '\Xfile'), s:normalize_fname(resolve('./Xlink')))
@@ -333,11 +334,14 @@
 
   " test for reparse point
   call mkdir('Xdir')
+  call assert_equal('Xdir', resolve('Xdir'))
   silent !mklink /D Xdirlink Xdir
   if !v:shell_error
     w Xdir/text.txt
+    call assert_equal('Xdir/text.txt', resolve('Xdir/text.txt'))
     call assert_equal(s:normalize_fname(getcwd() . '\Xdir\text.txt'), s:normalize_fname(resolve('Xdirlink\text.txt')))
     call assert_equal(s:normalize_fname(getcwd() . '\Xdir'), s:normalize_fname(resolve('Xdirlink')))
+    call delete('Xdirlink')
   else
     echomsg 'skipped test for reparse point'
   endif