SHS Simulator: Remove noise pattern if noise level is set to zero.

If noise is set != 0 and then ==0 afterwards, the noise pattern persists until another paramter is changed.

moved from shs#81

added u.eisenbarth/wombat~176 label

This belongs to SHS_common

closed

moved from u.eisenbarth/wombat#19

reopened

moved from shs_common#7 (moved)

mentioned in commit 68d5efab

closed via commit 68d5efab