rbd: move GetMappedID() to util package

This commit moves getMappedID() from rbd to util
package since it is not rbd specific and exports
it from there.

Signed-off-by: Rakshith R <rar@redhat.com>

internal/util/cluster_mapping_test.go

@@ -239,3 +239,55 @@ func validateMapping(t *testing.T, clusterID, rbdPoolID, cephFSPoolID string, ma
 
 	return nil
 }
+
+func TestGetMappedID(t *testing.T) {
+	t.Parallel()
+	type args struct {
+		key   string
+		value string
+		id    string
+	}
+	tests := []struct {
+		name     string
+		args     args
+		expected string
+	}{
+		{
+			name: "test for matching key",
+			args: args{
+				key:   "cluster1",
+				value: "cluster2",
+				id:    "cluster1",
+			},
+			expected: "cluster2",
+		},
+		{
+			name: "test for matching value",
+			args: args{
+				key:   "cluster1",
+				value: "cluster2",
+				id:    "cluster2",
+			},
+			expected: "cluster1",
+		},
+		{
+			name: "test for invalid match",
+			args: args{
+				key:   "cluster1",
+				value: "cluster2",
+				id:    "cluster3",
+			},
+			expected: "",
+		},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			val := GetMappedID(tt.args.key, tt.args.value, tt.args.id)
+			if val != tt.expected {
+				t.Errorf("getMappedID() got = %v, expected %v", val, tt.expected)
+			}
+		})
+	}
+}