Fix delay latency minimum: ubridge rejects latency <= 0

Align validation rules with ubridge source: delay latency must be > 0
(packet_filter.c delay_setup line 182). Update FILTERS definition in
link.py and test cases accordingly.

gns3server/controller/link.py

@@ -48,7 +48,7 @@ FILTERS = [
         "name": "Delay",
         "description": "Delay packets in milliseconds. You can add jitter in milliseconds (+/-) of the delay",
         "parameters": [
-            {"name": "Latency", "minimum": 0, "maximum": 32767, "unit": "ms", "type": "int"},
+            {"name": "Latency", "minimum": 1, "maximum": 32767, "unit": "ms", "type": "int"},
             {"name": "Jitter (-/+)", "minimum": 0, "maximum": 32767, "unit": "ms", "type": "int"},
         ],
     },