GuidedStep: Fix addAsRoot() restoring problem

Should only add fragment when savedInstanceState is not null.
Since Activity.onCreate(savedInstanceState) will restore
the FragmentManager and Framgnets.

This CL dumps a warning and skip creating fragment when detected
duplicated fragment.

Bug 27972030

Change-Id: Iaa3177b0b70877ffea25e49d44f5be778a734a55
2 files changed