[FIX] sap.m.ComboBox: prevent the text-editing pop-up to be open

- Prevent the text-editing pop-up to be open, text-editing
mode disturbs the usability experience (it blocks the UI in some
devices)

Change-Id: Idc334ca444232fe1ca0f83ea1a6b93df81395f3c
CSS: 0120031469 0000721248 2014
Merge "[FIX] sap.m.ComboBox: prevent the text-editing pop-up to be open"