tests: invoke full_cleanup from script trap handlers, use modprobe -r

Scripts implementing their own trap handlers override the generic
one provided by utils.sh (full_cleanup). Invoke it at the end of
the handlers to provide the utils cleanup as well.

Moreover, change use of "rmmod" to "modprobe -r", which is better
in trap handlers because it does not print errors if the module
was not loaded yet when the signal occurs.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>