Add tests for audits and flavor utilities, update .gitignore, and enhance CPU data handling

dashboard/openstack_utils/audits.py

@@ -11,6 +11,9 @@ from dashboard.prometheus_utils.query import query_prometheus
 def convert_cpu_data(data: list):
     metrics = []
 
+    if not data:
+        return pandas.DataFrame(columns=["host", "cpu_usage"])
+
     for entry in data:
         for t, val in entry["values"]:
             metrics.append({