Adapt alertmanager to dedicated storage network

Ref: https://github.com/harvester/harvester/issues/2715

criteria

PVCs (alertmanager/grafana/Prometheus) will attach back after dedicated storage network switched.

Verify Steps:

  1. Install Harvester with any nodes
  2. Navigate to Networks -> Cluster Networks/Configs, create Cluster Network named vlan, create Network Config for all nodes
  3. Navigate to Advanced -> Settings, edit storage-network
  4. Select Enable then select vlan as cluster network, fill in VLAN ID and IP Range
  5. Wait until error message (displayed under storage network setting) disappeared
  6. Navigate to Monitoring & Logging -> Monitoring -> Configuration
  7. Dashboard of Prometheus Graph, Grafana and Altertmanager should able to access, and should contain old data.