[FIX] sap.m.IconTabBar: Fix persisting the selected tab when the tab
doesn't have a key.

Change-Id: I4cf131a42e0be9e9edea2d9c51d06268fa2028e5
BCP: 1482007468
CR-Id: 012006153200014994912014
Merge "[FIX] sap.m.IconTabBar: Fix persisting the selected tab when the tab doesn't have a key." into rel-1.26