Try to check the platform decryption key is still accessible before

using the platform encryption key

Also did some small clean-up changes in the same files.

Test: adb shell am instrument -w -e package
com.android.server.locksettings.recoverablekeystore
com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner

Change-Id: If34ca756e7d9cf5e053786a87f14f59d482d0cf9