Remove prev SBIV parent before attaching to NIC

This fixes an edge case were the NotificationIconContainer is
re-inflated and re-bound due to a configuration change, and as a result
the SBIVs (which are re-used between the NIC instances) are still
attached to the prev container.

Flag: ACONFIG com.android.systemui.notifications_icon_container_refactor DEVELOPMENT
Fixes: 315396311
Test: manual - enable flag, change display size and text, verify no crash
Change-Id: I94c109bf0f14c3902f5c1534b9b74f4956dc1ce9