Give some time for pulseaudio to quit before restarting

This fix attempts to fix a race condition which was noticed when invoking "pulseaudio --kill" and then trying to restart the systemd service right after. When it fails, pulseaudio fails to restart with: E: [pulseaudio] pid.c: Daemon already running. E: [pulseaudio] main.c: pa_pid_file_create() failed.

This change adds a sleep after the kill command to give more time for pulseaudio to quit before attempting a restart.

Signed-off-by: Andre Moreira Magalhaes (andrunko) andre.magalhaes@collabora.co.uk