[Applet]Improvements for unavailable port.
Summary:
Restore capability of unavailable ports to be active, which was prevented
with 10ab204a62cf.
Enable port selection in case an unavailable port is active.
Test Plan:
Before: Choosing an unavailable port from pavucontrol was impossible.
After: Activating an unavailable port is possible. Can test with D27422.
Reviewers: Plasma, drosca, ngraham
Reviewed By: ngraham
Subscribers: pino, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D27420