Don't preload libneuralnetworks.so

The lib isn't used by most of the apps. Don't waste memory by preloading
it to all apps.

Bug: 142482121
Test: `lsof -p $(pidof zygote64) | grep libneuralnetwork` shows nothing
Change-Id: I4a6e3df838fa3b7a46271e548e9fdc87bea948ae