Only show the bouncer for the assistant if secure.

We do this by using the helpful tools in
KeyguardActivityLauncher which do all the right callbacks
and stuff.

(This assumes the assist gesture is sufficiently hard to
false that we don't need the extra step of bouncing the
glowpad unlock affordance.)

Bug: 7500637
Change-Id: Id68cb85cdfd741f43a5bce69118ec4209125d785