patch 8.0.1482: using feedkeys() does not work to test completion

Problem:    Using feedkeys() does not work to test Insert mode completion.
            (Lifepillar)
Solution:   Do not check for typed keys when executing :normal or feedkeys().
            Fix thesaurus completion not working when 'complete' is empty.
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index e57782f..652b1d9 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -116,3 +116,14 @@
   delfunc Omni
   set omnifunc=
 endfunc
+
+" Check that when using feedkeys() typeahead does not interrupt searching for
+" completions.
+func Test_compl_feedkeys()
+  new
+  set completeopt=menuone,noselect
+  call feedkeys("ajump ju\<C-X>\<C-N>\<C-P>\<ESC>", "tx")
+  call assert_equal("jump jump", getline(1))
+  bwipe!
+  set completeopt&
+endfunc