Handle Agent without host (#1443)

Usually the host being checked is not terminated. However there might be some synchronization latency. Mark it as not stale and we will handle it in the next run.
This will reduce error budget noise.

deploy-service/teletraanservice/src/main/java/com/pinterest/teletraan/worker/AgentJanitor.java

@@ -121,11 +121,17 @@ private boolean isHostStale(HostAgentBean hostAgentBean) {
 
         HostBean hostBean;
         try {
-            hostBean = hostDAO.getHostsByHostId(hostAgentBean.getHost_id()).get(0);
+            List<HostBean> hostBeans = hostDAO.getHostsByHostId(hostAgentBean.getHost_id());
+            if (hostBeans.isEmpty()) {
+                // Usually the host being checked is not terminated. However there might be some
+                // synchronization latency.
+                // Mark it as not stale and we will handle it in the next run.
+                return false;
+            }
+            hostBean = hostBeans.get(0);
         } catch (Exception ex) {
             LOG.error("failed to get host bean for ({}), {}", hostAgentBean, ex);
             errorBudgetFailure.increment();
-
             return false;
         }