Always position home stack either at the top or bottom of the list.

The current implementation was okay since we mostly had
2 stacks (the home stack and 1 application stack), so moving the
application stack to the top meant the home stack was automatically
moved to the bottom. This is no longer the case if you have multiple
application stacks.

Change-Id: I8ec7cfdc3650a73a00c4e8dad869fb2bec2a4eac