Do not remove auto-created not-yet-logged-in ephemeral guest users during boot.

We don't need to remove this type ephemeral users because:
1. It will be recreated again anyway.
2. It doesn't have any user data because it hasn't been switched to yet.

This avoids unnecessary operations, and improves boot duration.

Bug: 341165986
Change-Id: Id5d3659ad3377e85a901c0d7ef706ff615eb765b
Test: atest CtsMultiUserHostTestCases
Flag: EXEMPT bugfix