monitoring: fix CephPoolGrowthWarning expression

Prometheus found duplicate series for the match group `pool_id`
and `instance` when evaluating the CephPoolGrowthWarning alert
expression. This alert has an evaluation interval of 2 days and
did not consider the changing POD names during the Rook migration process.

This commit adds the `pod` label to the set of considered labels.

Signed-off-by: Matej Feder <matej.feder@dnation.cloud>
(cherry picked from commit 6ba084f)

deploy/charts/rook-ceph-cluster/prometheus/localrules.yaml

@@ -533,7 +533,7 @@ groups:
         annotations:
           description: "Pool '{{ $labels.name }}' will be full in less than 5 days assuming the average fill-up rate of the past 48 hours."
           summary: "Pool growth rate may soon exceed capacity"
-        expr: "(predict_linear(ceph_pool_percent_used[2d], 3600 * 24 * 5) * on(pool_id, instance) group_right() ceph_pool_metadata) >= 95"
+        expr: "(predict_linear(ceph_pool_percent_used[2d], 3600 * 24 * 5) * on(pool_id, instance, pod) group_right() ceph_pool_metadata) >= 95"
         labels:
           oid: "1.3.6.1.4.1.50495.1.2.1.9.2"
           severity: "warning"

deploy/examples/monitoring/localrules.yaml

@@ -537,7 +537,7 @@ spec:
           annotations:
             description: "Pool '{{ $labels.name }}' will be full in less than 5 days assuming the average fill-up rate of the past 48 hours."
             summary: "Pool growth rate may soon exceed capacity"
-          expr: "(predict_linear(ceph_pool_percent_used[2d], 3600 * 24 * 5) * on(pool_id, instance) group_right() ceph_pool_metadata) >= 95"
+          expr: "(predict_linear(ceph_pool_percent_used[2d], 3600 * 24 * 5) * on(pool_id, instance, pod) group_right() ceph_pool_metadata) >= 95"
           labels:
             oid: "1.3.6.1.4.1.50495.1.2.1.9.2"
             severity: "warning"