ctdb-tests: Avoid early exits in scripts that appear on tail of a pipe

ctdb-tests: Avoid early exits in scripts that appear on tail of a pipe

When executing a shell script code "foo | bar", if "bar" terminates early,
then "foo" can get I/O error when writing to stdout.

The tdbtool stub did not wait to read anything from stdin when it is
expected to.  This would cause tests to fail randomly under load when
tdbtool process exited early.

Similarly, debug function read from stdin only under certain conditions
(higher debug and when not reading from tty).  Otherwise, exited early.

Thanks to Andrew Bartlett for noticing the problem and Catalyst Cloud
(http://catalyst.net.nz/cloud) for providing resources to test fixes.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Pair-Programmed-With: Martin Schwenke <martin@meltin.net>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Michael Adam <obnox@samba.org>
Autobuild-Date(master): Fri Mar 20 16:26:37 CET 2015 on sn-devel-104