tests: Reduce sleep in regression/tools/clear/test_ust

tests: Reduce sleep in regression/tools/clear/test_ust

Motivation
==========

This test is one of the longer running non-kernel
non-destructive tests, taking ~7 minutes to run
in my development environment.

Solution
========

By reducing the the sleeps from a half second to a tenth of a second,
the test passes from 364.0s to 309.1s.

Known drawbacks
===============

None

Signed-off-by: Kienan Stewart <kstewart@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Ibe6c37d474edf5ca118c82669e073089d888ff84