[FIX] sap.m.Popover: Do not use jQuery dimension methods on init.
[FIX] sap.m.Popover: Do not use jQuery dimension methods on init.

There are some edge cases where the browser jumps/scrolls across
the page when jQuery(window).width() and jQuery(window).height()
methods are used in Poppover's init method.
Moving those calculations to onBeforeRendering as they'd be used
right after the rendering.

BCP: 0020751294 0000174462 2017

Change-Id: I5b583515a8629498f7c6bc3931b4ac4529d753af

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