Add a specific error code for keystore failure

Because of the keystore 2.0 migration, we expect to see one time RoR
failures in S build. Add an error code to distinguish the case.

Bug: 183140900
Test: atest FrameworksServicesTests:RebootEscrowManagerTests
Change-Id: Ieeb0ebef570cb7392f6ac47d2ad918da64869712