Add get_auth_token permission to allow credstore to call keystore2.

This CL adds a new keystore2 permission "get_auth_token"and grants this
permission to credstore which needs to call keystore2 to obtain
authtokens.

Bug: 159475191
Test: CtsVerifier
Change-Id: I1c02ea73afa6fe0b12a2d74e51fb4a8a94fd4baf
2 files changed