Rewrite not-yet-covered dejagnu tests in Python

Rewrite not-yet-covered dejagnu tests in Python

Remove the dejagnu scripts gssapi.exp, princexpire.exp, sample.exp,
simple.exp, and tcp.exp.

Add server output checking to t_gss_sample.py to match the checks in
gssapi.exp.

Add a test to t_general.py matching the #6428 regression test in
princexpire.exp.

Add new test scripts t_sample.py and t_simply.py for the appl/sample
and appl/simple applications, to match sample.exp and simple.exp.
Adjust the simple and sample servers to allow for startup detection
when stdout is a pipe.  Both of these test servers exit after one
client execution; add a k5test function await_daemon_exit() to allow
the daemon exit status to be checked without sending a kill signal.
Change start_in_inetd() not to require the program name to be
specified twice.  Adjust the existing t_user2user.py for the
aforementioned changes.

Add a TCP test to t_bigreply.py to match the oversized-TCP-request
test in tcp.exp.  The existing t_bigreply.py test already covers a
successful TCP request.