patch 8.2.3886: can define autocmd for every event by using "au!"

Problem:    Can define autocmd for every event by using "au!".
Solution:   Check if a command is present also for "au!".
diff --git a/src/testdir/test_arglist.vim b/src/testdir/test_arglist.vim
index ca7e2f8..9f9957a 100644
--- a/src/testdir/test_arglist.vim
+++ b/src/testdir/test_arglist.vim
@@ -581,7 +581,7 @@
 
 func Test_clear_arglist_in_all()
   n 0 00 000 0000 00000 000000
-  au! * 0 n 0
+  au WinNew 0 n 0
   call assert_fails("all", "E1156")
   au! *
 endfunc
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 4bdb8dc..b6f621d 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
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