[FIX] playing sound was not working

It seems that the removal of the IMBeepAction also removed
the code to activate/deactivte the sound. Changed the
preference store so the SoundPlayer will again fetch the
right value to check if playing sound is enabled or disabled.
	 

Change-Id: I707ae0e8632ffc66553a007f9afdbfd5f8ffd94d
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1036
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>