Test basic_login_session_cache_test is flakey

[ximon18]

From: https://github.com/NLnetLabs/krill/actions/runs/6508984037/job/17679444611#step:5:882

---- daemon::auth::common::session::tests::basic_login_session_cache_test stdout ----
thread 'daemon::auth::common::session::tests::basic_login_session_cache_test' panicked at src/daemon/auth/common/session.rs:332:9:
assertion `left == right` failed
  left: 0
 right: 1
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

This failed in a test run in which the changes made seem unrelated to the failure.

[ximon18]

The test is dependent on elapsed time which in a CI environment with slower and shared-tenancy machines is going to be unreliable. A proper fix will require removing the dependence on elapsed time.