[NUI] Fix RadioButton not to invoke duplicate SelectedChanged (#2115)
RadioButton does not change its state to unselected if button or key is
unpressed while its state is selected.
Previously, RadioButton invoked duplicate SelectedChanged if button or
key is unpressed while its state is selected.
Now, RadioButton does not invoke duplicate SelectedChanged if button or
key is unpressed while its state is selected.
Co-authored-by: Jaehyun Cho <jae_hyun.cho@samsung.com>
Co-authored-by: Jiyun Yang <ji.yang@samsung.com>