Increase the timeout for HostUnreachable

Require more ICMP probes to fail before the alert triggers.

roles/float-infra-prometheus/templates/rules/alerts_base.conf.yml

@@ -9,7 +9,7 @@ groups:
   # might fire immediately after the transition.
   - alert: HostUnreachable
     expr: min_over_time(host_reachable[10m]) == 0
-    for: 1m
+    for: 2m
     labels:
       severity: warn
     annotations: