tests/pty.sh: fix two failures due to typeahead on Debian Bullseye

As the (original AT&T) comment at the top says, "the trickiest part
of the tests is avoiding typeahead in the pty dialogue".

Two tests failed to [p]eek at the prompt before they started
'typing'. This causes unpredictable results. On Debian Bullseye
this triggers typeahead, which produces unwanted echo to the
terminal, killing the tests.

src/cmd/ksh93/tests/pty.sh:
- Add missing 'p' commands for the first prompt to the tests
  'nobackslashctrl in emacs' and 'emacs backslash escaping'.

Resolves: https://github.com/ksh93/ksh/issues/332

src/cmd/ksh93/tests/pty.sh

@@ -628,6 +628,7 @@ r ^:test-2:
 L nobackslashctrl in emacs
 
 d 15
+p :test-1:
 w set -o emacs --nobackslashctrl
 
 # --nobackslashctrl shouldn't be ignored by reverse search
@@ -641,6 +642,7 @@ r ^:test-2: \r\n$
 L emacs backslash escaping
 
 d 15
+p :test-1:
 w set -o emacs
 
 # Test for too many backslash deletions in reverse-search mode