Add a product flavor to build APK target API 25
Add a product flavor to build APK target API 25

APK targeting O must be "test only" and can only be installed in O+
devices.

Let's have two build variants temporarily until the restriction is gone

Change-Id: I6d4fcaca96bb1dbbb06a07f515d75e05ee967da1

googlesamples/android-testdpc,googlesamples/android-testdpc