[FIX] sap.m.Tree: Should get the expanded state from the binding
[FIX] sap.m.Tree: Should get the expanded state from the binding

- When the factory function is used controls are destroyed and created
from scratch therefore we should get the expanded state from the binding
the control might have been destroyed already.

BCP: 0020751294 0000663749 2018

Change-Id: I948fdf44a2a7e8ce0736e3eb59f5d49bbeba6a48

SAP/openui5,SAP/openui5,SAP/openui5,SAP/openui5