Add optional obsolete files for the installworld without sendmail

Add two more entries for WITHOUT_SENDMAIL install. The /var/spool/clientmqueue
entry would be deleted only if there are no files/dirs in it, so the
content generated during previous lifecycle of the system is safe

PR: 228484
Submitted by: Dmitry Wagin <dmitry.wagin@ya.ru>
MFC after: 1 week