tap: log all TAP stream, even after a "Bail out!"

tap: log all TAP stream, even after a "Bail out!"

* lib/tap-driver ($bailed_out): New global boolean variable,
telling whether a "Bail out!" directive has been seen or not.
(handle_tap_bailout): This function does not anymore stop the
reading from TAP stream; instead, it sets `$bailed_out' to a
true value, so that only the subsequent parsing of the input
TAP stream is stopped.
(finish): Remove, no more needed, its contents inlined into ...
(main): ... this function, with related adjustments in the code
flow.
(get_test_exit_message): Do not "flush" the input TAP stream
to fetch the exit status of test script, it is not anymore
required.  Add a sanity check.
* tests/tap-bailout-and-logging.test: New test.
* tests/Makefile.am (tap_with_common_setup_tests): Update.