Add userId to RecoverableKeyStoreDb

We need to store the userId (i.e., the uid of the *profile*, not the
app), as well as the app uid. This is because when the screen is
unlocked, the unlock is associated with a specific user profile, not
a specific app. So at that point we need to look up all keys that
are pending sync for that *user*, and upload them to the remote
storage.

Test: adb shell am instrument -w -e package com.android.server.locksettings.recoverablekeystore com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner
Change-Id: I6c456cca8974f5e1a15dfde6e9dd4e6bf4c16065