Update the detection method for docker overlay2 issue

Author: wangzhen127

config/docker-monitor.json

@@ -7,12 +7,24 @@
 	"lookback": "5m",
 	"bufferSize": 10,
 	"source": "docker-monitor",
-	"conditions": [],
+	"conditions": [
+		{
+			"type": "CorruptDockerOverlay2",
+			"reason": "NoCorruptDockerOverlay2",
+			"message": "docker overlay2 is functioning properly"
+		}
+	],
 	"rules": [
 		{
 			"type": "temporary",
 			"reason": "CorruptDockerImage",
 			"pattern": "Error trying v2 registry: failed to register layer: rename /var/lib/docker/image/(.+) /var/lib/docker/image/(.+): directory not empty.*"
+		},
+		{
+			"type": "permanent",
+			"condition": "CorruptDockerOverlay2",
+			"reason": "CorruptDockerOverlay2",
+			"pattern": "returned error: readlink /var/lib/docker/overlay2.*: invalid argument.*"
 		}
 	]
 }