Use /healthz for liveness and readiness probes in beacon chain (#2180)

* lower the p2p peer count minimum for a successful status

* add liveness and health probes

* 5m instead of 2m

k8s/beacon-chain/beacon-chain.deploy.yaml

@@ -77,8 +77,17 @@ spec:
                   key: DEPOSIT_CONTRACT_ADDRESS
           readinessProbe:
             initialDelaySeconds: 60
-            tcpSocket:
-              port: 4000
+            httpGet:
+              path: /healthz
+              port: 9090
+          livenessProbe:
+            initialDelaySeconds: 60
+            failureThreshold: 30 # Fails consistently for 5 minutes
+            periodSeconds: 10
+            httpGet:
+              path: /healthz
+              port: 9090
+
   volumeClaimTemplates:
   - metadata:
       name: beacondb