rbd: use clusterID from volumeContext at nodestage

previously we were retriving clusterID using the monitors field
in the volume context at node stage code path. however it is possible to
retrieve or use clusterID directly from the volume context. This
commit also remove the getClusterIDFromMigrationVolume() function
which was used previously and its tests

Signed-off-by: Humble Chirammal <hchiramm@redhat.com>

internal/util/csiconfig.go

@@ -161,47 +161,3 @@ func GetClusterID(options map[string]string) (string, error) {
 
 	return clusterID, nil
 }
-
-// GetClusterIDFromMon will be called with a mon string to fetch
-// clusterID based on the passed in mon string. If passed in 'mon'
-// string has been found in the config the clusterID is returned,
-// else error.
-func GetClusterIDFromMon(mon string) (string, error) {
-	clusterID, err := readClusterInfoWithMon(CsiConfigFile, mon)
-
-	return clusterID, err
-}
-
-func readClusterInfoWithMon(pathToConfig, mon string) (string, error) {
-	var config []ClusterInfo
-
-	// #nosec
-	content, err := ioutil.ReadFile(pathToConfig)
-	if err != nil {
-		err = fmt.Errorf("error fetching configuration file %q: %w", pathToConfig, err)
-
-		return "", err
-	}
-
-	err = json.Unmarshal(content, &config)
-	if err != nil {
-		return "", fmt.Errorf("unmarshal failed (%w), raw buffer response: %s",
-			err, string(content))
-	}
-
-	for _, cluster := range config {
-		// as the same mons can fall into different clusterIDs with
-		// different radosnamespace configurations, we are bailing out
-		// if radosnamespace configuration is found for this cluster
-		if cluster.RadosNamespace != "" {
-			continue
-		}
-		for _, m := range cluster.Monitors {
-			if m == mon {
-				return cluster.ClusterID, nil
-			}
-		}
-	}
-
-	return "", ErrMissingConfigForMonitor
-}