[INTERNAL]: sap.m.IconTabBar: Remove content aggregation in unit test
[INTERNAL]: sap.m.IconTabBar: Remove content aggregation in unit test

Also, call sap.ui.core.Core#applyChanges method to clear the
destroyed control from the screen at the end of the test.

Change-Id: Iea83c790968b28c879c8de1fae4c7a68a545b6f7
JIRA: BGSOFUIRODOPI-2528

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