patch 8.1.0055: complete test has wrong order of arguments

Problem:    Complete test has wrong order of arguments. Wrong type for
            sentinel variable.
Solution:   Swap arguments, use VAR_UNKNOWN. (Ozaki Kiichi)
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index 2b4356e..2cd29b5 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -126,15 +126,15 @@
 
   set completefunc=CompleteFunc
   call feedkeys("i\<C-X>\<C-U>\<Esc>", 'x')
-  call assert_equal(s:args[0], [1, 1])
-  call assert_equal(s:args[1][0], 0)
+  call assert_equal([1, 1], s:args[0])
+  call assert_equal(0, s:args[1][0])
   set completefunc=
 
   let s:args = []
   set omnifunc=CompleteFunc
   call feedkeys("i\<C-X>\<C-O>\<Esc>", 'x')
-  call assert_equal(s:args[0], [1, 1])
-  call assert_equal(s:args[1][0], 0)
+  call assert_equal([1, 1], s:args[0])
+  call assert_equal(0, s:args[1][0])
   set omnifunc=
 
   bwipe!