When launching home activity, make sure it is top.

Because recents sits on the same stack as launcher it can sometimes be
above launcher. When we were launching home activity because the flag
told us to we would sometimes launch recents instead. This fix makes
sure that the home activity is on the top when it is supposed to be
launched next.

Previously this was fixed by having recents move itself to the back
of the stack after it launched an activity (b/9750207 and ag/336019).
But that solution caused the AppTransition to be set to
TRANSIT_TASK_TO_BACK which left the SOFT_INPUT_IS_FORWARD_NAVIGATION
flag unset. This in turn caused IMEs to remain unlaunched when
returning from recents (b/10240567).

Fixes bug 10240567.

Change-Id: I35c6619af0e68d0e6d9ab87cad06ea7c27e11e27