Disable kernel UID updates until update lands.

Current prebuilt kernel can result in the framework banging its head
against the wall writing the first duplicate update; it does this by
returning 0 for write().

We can revert this or flip the flag once an updated kernel lands.

Test: builds, boots
Bug: 33755020
Change-Id: Idb3e5ad40e2e6681848b47ce2b29dff9db3d4f6f