[FIX] core.HTML: Render content correctly on switching visibility

Fixes https://github.com/SAP/openui5/issues/231
CR-Id: 012003146900009383162014
Change-Id: I7fe4355d4a8a4c6dc8d8a70cb364f9dfbb4c5d5e
Merge "[FIX] core.HTML: Render content correctly on switching visibility" into rel-1.26