[ORKHeightPicker] Fix previous answer not being remembered
[ORKHeightPicker] Fix previous answer not being remembered

The _answerFormat ivar needs to be properly set before for the self.answer setter to work correctly.

chb/ResearchKit,weijentu/ResearchKit,md0u80c9/ResearchKit,boland25/ResearchKit,chb/ResearchKit,oliverschaefer/ResearchKit,oliverschaefer/ResearchKit,boland25/ResearchKit,mluedke2/ResearchKit,weijentu/ResearchKit,YuanZhu-apple/ResearchKit,YuanZhu-apple/ResearchKit,jeremiahyan/ResearchKit,cornelltech/ResearchKit,oliverschaefer/ResearchKit,boland25/ResearchKit,boland25/ResearchKit,YuanZhu-apple/ResearchKit,chb/ResearchKit,jeremiahyan/ResearchKit,chb/ResearchKit,weijentu/ResearchKit,md0u80c9/ResearchKit,weijentu/ResearchKit,mluedke2/ResearchKit,cornelltech/ResearchKit,oliverschaefer/ResearchKit,md0u80c9/ResearchKit,cornelltech/ResearchKit,jeremiahyan/ResearchKit,mluedke2/ResearchKit,YuanZhu-apple/ResearchKit,md0u80c9/ResearchKit