Fix incorrect calc of GetHeightForWidth in TextLabel
the recent change of CalculateLayoutSizeOnRequiredControllerSize()
causes compatibility issues in TextLabel.
avoiding backup/restore of visual-model fields after GetNaturalSize/GetHeightForWidth is
usually to resolve broken index of editable controls.
this patch DoRelayout() with minimal operation when non-editable case.
it's almost like legacy code.
Change-Id: Ib918c96ad45fc3567941bec17dffe910b8b45134
Signed-off-by: Bowon Ryu <bowon.ryu@samsung.com>