Cleanup Perforce test case, and thereby its output a little.

Summary: Making the test code a little cleaner by using TestCore::self()

Test Plan: Tests execute as before, output is now not cluttered with init related stuff

Reviewers: KDevelop, kfunk

Reviewed By: KDevelop, kfunk

Subscribers: kdevelop-devel

Tags: KDevelop

Differential Revision: https://phabricator.kde.org/D14959

(cherry picked from commit 2e98de947febd5297475c22b35ac390ed693de5b)