[Applet/TaskManager]Don't create extra PulseAudio component
Summary: Use the component already created.
Test Plan:
Functionality must stay the same.
Test with D27684's Test Plan.
Also test without plasma-pa, no options or icon should appear,
without any warning.
Reviewers: Plasma, hein, ngraham
Reviewed By: ngraham
Subscribers: broulik, ngraham, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D27734