[DO NOT MERGE] Backup account access grants

Sync adapters without an account access cannot run until the
user approves the account access (for the case the account
access is not allowed by other policy such as being singed
with the same cert as the authenticator). If the sync adapter
does not have permission to access the account we ask the
user to grant access and take a note. This CL adds backup
for the explicit user grants.

bug:31162498

Change-Id: I31e3f3d010475352c7c54255ac2d3a2fed4d0c72