Dialer: Only when the phone state is idle, hide the dialpad chooser

When reenter the DialtactsActivity, because phone state is offhook,
it should show dialpad chooser, but immediately due to sub2's call
state is idle, then the dialpad chooser is hidden.

Only when the phone state is idle, we hide the dialpad chooser.

Change-Id: I9eeecff316a6e658ceb278473550865f249980e1
CRs-Fixed: 809521