Add monitoring in tent

Reviewed-by: Aleix Boné <abonerib@bsc.es>
Reviewed-by: Aleix Roca Nonell <aleix.rocanonell@bsc.es>

m/tent/blackbox.yml

@@ -0,0 +1,13 @@
+modules:
+  http_2xx:
+    prober: http
+    timeout: 5s
+    http:
+      follow_redirects: true
+      valid_status_codes: []  # Defaults to 2xx
+      method: GET
+  icmp:
+    prober: icmp
+    timeout: 5s
+    icmp:
+      preferred_ip_protocol: "ip4"