libtaskmanager: add unit test for BUG 444816
Bug description: A launcher item will jump back to the old position when user tries to move it to a position between running tasks when "Keep launchers separate option" is disabled.
Edited by Fushan Wen
Bug description: A launcher item will jump back to the old position when user tries to move it to a position between running tasks when "Keep launchers separate option" is disabled.