Use correct packageName for checking if it belongs to callingUid.

In AccountManagerService.getAccountsAsUser, we check if opPackageName
belongs to calling uid by calling AppOpsManager.checkPackage. But when
AccountManagerService.getAccountsAsUser is called from
AccountManagerService.addSharedAccountsFromParentUser, we're using the
opPackageName from system context instead of calling context.

Bug: 35258008
Test: cts-tradefed run singleCommand cts-dev --module CtsMultiUserHostTestCases \
      -t android.host.multiuser.CreateUsersPermissionTest#testCanCreateRestrictedUser
Change-Id: I5c425d9314beb86f7c64a5b5c64b7d879711879a