Do not spuriously alter image-synchro list.
Do not spuriously alter image-synchro list.

(Looks like the current shutter used to be added to image synchro
automatically, and unconditionally removed when no longer the current
shutter.)

git-svn-id: 03a8048b5ee8463be5048a3801110fb50f378627@13703 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd

kmdouglass/Micro-Manager,kmdouglass/Micro-Manager