ctdb-tests: Don't expand octal escapes in unit test output

ctdb-tests: Don't expand octal escapes in unit test output

The echo command in dash expands octal escapes in strings by default
but the echo command in bash doesn't.  Since the behaviour is
ill-defined, use printf to handle affected strings.  However, ensure
that these strings aren't used as format strings.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
Autobuild-User(master): Amitay Isaacs <amitay@samba.org>
Autobuild-Date(master): Tue Mar 27 09:06:14 CEST 2018 on sn-devel-144