[INTERNAL][FIX] sap.uxap.ObjectPageLayout: Cleanup of scheduled tasks on exit
[INTERNAL][FIX] sap.uxap.ObjectPageLayout: Cleanup of scheduled tasks on exit

The problem: When control.destroy() is called before control's internaly scheduled tasks managed to execute
=> these taks will still execute later *but on a destroyed instance*
=> errors are thrown because the control is in an inconsistent state
Fixed by cancelling scheduled tasks upon dectruction of the control.

Change-Id: Icd9bddd74152a25584b793b43d0d887c15dd1367
BCP: 1780319799

nzamani/openui5,cschuff/openui5,SAP/openui5,SAP/openui5,SQCLabs/openui5,SQCLabs/openui5,SAP/openui5,nzamani/openui5,cschuff/openui5,SAP/openui5,nzamani/openui5,cschuff/openui5,SQCLabs/openui5