Ignore the optimized location passed to DexFile.loadDex()

This ensures that apps don't trigger dex2oat to locations
that are not recognized (anymore) by the runtime.

The background compilation job will takes care of optimizing
the dex files loaded via DexClassLoader.

Test: m test-art-host
Bug: 36824842

(cherry picked from commit 1f7079b7)

Change-Id: Icf07ac70b5d2df7b9e6259877908d12b96827a82