The test is incorrect.

Change-Id: I4e4b788f34e01f926d60d97515de4191d7346d5e
Unregister all listeners first then re-register them.

It's safe this way in case we are transferring them within the same
column.  Any empty broadcasters are checked and purged at the end.

Change-Id: Ib2d46e616cde4923720ad21cb101d3a97dc8c5d9