package/pulseaudio: fix S50pulseaudio init script

- fix the following start warnings:

  W: [pulseaudio] main.c: Running in system mode, but --disallow-exit not set.
  W: [pulseaudio] main.c: Running in system mode, but --disallow-module-loading not set.
  N: [pulseaudio] main.c: Running in system mode, forcibly disabling SHM mode.
  N: [pulseaudio] main.c: Running in system mode, forcibly disabling exit idle time.

- fix the following stop error:

  E: [pulseaudio] main.c: Failed to kill daemon: No such process

Signed-off-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>