Permit duplicate atoms in logging tests

This test fails on devices with multiple primary users because an atom
is sent for each (user, source) tuple and the assertion was written
assuming only one user.

A known downside of this change is that it will no longer fail if
multiple duplicate atoms are sent per user per source and I may
address this in a later CL.

Fix: 290570670
Relnote: N/A
Test: See bug
Change-Id: Ic1939e6bbe53be370261e68d7c80a3671b7f479b