Do not use empty UserInfo constructor

The UserInfo() constructor is not safe, since it does not set the
mandatory fields. It should not be used. Right now it is used in some
tests, so we cannot remove it yet. But we mark that it should not
be used.

Test: N/A (just comments/annotations)
Bug: 142482943
Change-Id: I2f70a8d372c2e2bcd0e136cfe7ff76f9756dddeb