This test of silence cleanup was flaky because of its use of real wall
time. In CI environments with slow execution, delays could cause the
test to fail. This change mitigates the problem by increasing the end time of
silences in the test.
After Prometheus merges this PR: https://github.com/prometheus/alertmanager/pull/2867
we can make the test fully deterministic by using a fake clock.
Fixes#47470
Signed-off-by: Joe Blubaugh <joe.blubaugh@grafana.com>
Joe Blubaugh
631dd718a2