Viewer issue

see https://trac.openmicroscopy.org.uk/ome/ticket/11975 and https://trac.openmicroscopy.org.uk/ome/ticket/11974

To test
* Log in as user-1
* Expand archivedv
* Open an image with multi Z and multi T
* Turn on all channels
* Play T movie (click on arrow next to slider). Make sure the channels are not turned off.
* Play Z movie (click on arrow next to slider). Make sure the channels are not turned off.