Add relabel for alerts with only job or host

Change-Id: If96fcc3d0bdbfa724e468cb03a3ef3d56de414d8
Closes-Bug: PROD-20602
diff --git a/prometheus/server/alert/alerta_relabel.yml b/prometheus/server/alert/alerta_relabel.yml
index a81c59a..ca0f4b4 100644
--- a/prometheus/server/alert/alerta_relabel.yml
+++ b/prometheus/server/alert/alerta_relabel.yml
@@ -11,9 +11,15 @@
           - replacement: "aggregated"
             source_labels: "instance"
             target_label: "instance"
+          - source_labels: "host"
+            target_label: "instance"
+            regex: "(.+)"
+          - source_labels: "job"
+            target_label: "instance"
+            regex: "(.+)"
           - source_labels: ["host", "job"]
             target_label: "instance"
-            regex: "([a-zA-Z0-9]+;[a-zA-Z0-9_]+)"
+            regex: "(.+;.+)"
           - source_labels: ["hostname", "job"]
             target_label: "instance"
-            regex: "([a-zA-Z0-9]+;[a-zA-Z0-9_]+)"
+            regex: "(.+;.+)"
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