Implement addAuthToken method of IKeystoreAuthorization AIDL interface.

This CL adds only addAuthToken method. Remaining methods will be added
in the upcoming seperate CLs, so that each of them can land
independently.

Bug: 159475191
Test: TBD
Change-Id: I4a092119c45e8ea1eb7e3564a62c4689f32f4025
6 files changed