ctdb-tests: Don't run valgrind or other tracing in simple_test_command()

ctdb-tests: Don't run valgrind or other tracing in simple_test_command()

This function is used to run a extra command to check a result.  This
command is usually a script (often a stub) or an external command, so
no need to trace it with valgrind or whatever else might be specified.
In the worst case the command being run is a shell function, which
valgrind won't be able to find.

There is little use running the event script tests under valgrind.
However, when the whole test suite is being run under valgrind then it
should work.

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): Mon Sep  3 14:04:00 CEST 2018 on sn-devel-144