neverallow ueventd to set properties

Add a compile time assertion that no SELinux rules exist which
allow ueventd to set properties, or even connect to the property
socket.

See https://android-review.googlesource.com/#/c/133120/6/init/devices.cpp@941
for details.

Change-Id: Ia9e932a3d94443d70644b14f36c74df4be7e9e32