Don't execute Runnables after host activity is destroyed

Use Activity.isFinishing() to detect if an activity is (or will soon
be) destroyed.

Also use FragmentTransaction.commitAllowingStateLoss() instead of commit()
in ContactDetailLayoutController.initialize(), which can be called from
Handler.post().
(And removed TODOs related to this.)

Bug 5032952

Change-Id: Ib5598a3e0a94adeaafd0497ac54518f2c6634603