Check account type returned by AbstractAccountAuthenticator.

AccountManagerService already knows which account is used during
AbstractAccountAuthenticator.getAuthToken.

KEY_ACCOUNT_NAME and KEY_ACCOUNT_TYPE in the response look unnecessary,
but we can't change API at this moment.

Bug: 364269936
Test: manual
Flag: EXEMPT bugfix
Change-Id: Ifc62866f4feaca43abc32bc542b97f3741953f56