[ceph-operations] exclude /dev/loop in CephNodeRootFilesystemFull (#77)

* [ceph-operations] exclude `/dev/loop` in CephNodeRootFilesystemFull

* Apply suggestions from code review

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

Author: defo89

charts/ceph-operations/Chart.yaml

@@ -2,7 +2,7 @@ apiVersion: v2
 name: ceph-operations
 description: Ceph operations bundle
 type: application
-version: 1.8.19
+version: 1.8.20
 maintainers:
   - name: sumitarora2786
   - name: richardtief

charts/ceph-operations/alerts/nodes.yaml

@@ -6,7 +6,7 @@ groups:
   rules:
 {{- if not (.Values.prometheusRules.disabled.CephNodeRootFilesystemFull | default false) }}
   - alert: CephNodeRootFilesystemFull
-    expr: node_filesystem_avail_bytes{mountpoint="/"} / node_filesystem_size_bytes{mountpoint="/"} * 100 < 5
+    expr: node_filesystem_avail_bytes{mountpoint="/", device!~"/dev/loop.*"} / node_filesystem_size_bytes{mountpoint="/", device!~"/dev/loop.*"} * 100 < 5
     for: 5m
     labels:
       service: ceph