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
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:a3788486f2c7f728721c9700f7485f865b462609)
Merged-In: Ifc62866f4feaca43abc32bc542b97f3741953f56
Change-Id: Ifc62866f4feaca43abc32bc542b97f3741953f56