hdajackretask: Fix killing PulseAudio on newer PulseAudio versions

The standard configuration directory for PulseAudio has changed,
I think since 3.0. Adjust the directory lookup mechanism to match.

Signed-off-by: David Henningsson <david.henningsson@canonical.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>