Fix: tests: extra arguments are not passed to the remove trigger command

Fix: tests: extra arguments are not passed to the remove trigger command

Observed issue
==============
CI root jobs fails on the remove trigger operation for the user_trigger
trigger during the test_ust_notifier_discarded_count_multi_uid test.

Cause
=====
The `--owner uid` option and its argument are not passed during the
command execution.

Solution
========
Pass all extra parameters for the command execution.

Known drawbacks
=========

None.

Signed-off-by: Jonathan Rajotte <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Ic7b5d46b6793cda16a474c5459f9bf533812fe61