Fixed issue leading to state loss about child fragments

Fragments may now access the child fragment manager in
onCreate(). This ensures that fragments that exist in the
back stack have an opportunity to call
getChildFragmentManager().putFragment() and hence save
state that includes references to child fragments in a
reliable fashion.

NOTE: onCreateView() is not called for fragments in the
back stack.

Change-Id: Ib18402c336b10cd0e1e1f412a0e6acadfb9d4998
Merge "Fixed issue leading to state loss about child fragments" into du44