Fix kernel monitor issues:

* Change `unregister_netdevice` to be an event to fix #47.
* Change `KernelPanic` to `KernelOops` because we can't handle kernel
panic currently.
* Use system boot time instead of "StartPattern" to fix #48.

config/kernel-monitor.json

@@ -1,8 +1,7 @@
 {
 	"plugin": "journald",
 	"logPath": "/var/log/journal",
-	"lookback": "10m",
-	"startPattern": "Initializing cgroup subsys cpuset",
+	"lookback": "5m",
 	"bufferSize": 10,
 	"source": "kernel-monitor",
 	"conditions": [
@@ -25,12 +24,17 @@
 		},
 		{
 			"type": "temporary",
-			"reason": "KernelPanic",
+			"reason": "UnregisterNetDevice",
+			"pattern": "unregister_netdevice: waiting for \\w+ to become free. Usage count = \\d+"
+		},
+		{
+			"type": "temporary",
+			"reason": "KernelOops",
 			"pattern": "BUG: unable to handle kernel NULL pointer dereference at .*"
 		},
 		{
 			"type": "temporary",
-			"reason": "KernelPanic",
+			"reason": "KernelOops",
 			"pattern": "divide error: 0000 \\[#\\d+\\] SMP"
 		},
 		{
@@ -44,12 +48,6 @@
 			"condition": "KernelDeadlock",
 			"reason": "DockerHung",
 			"pattern": "task docker:\\w+ blocked for more than \\w+ seconds\\."
-		},
-		{
-			"type": "permanent",
-			"condition": "KernelDeadlock",
-			"reason": "UnregisterNetDeviceIssue",
-			"pattern": "unregister_netdevice: waiting for \\w+ to become free. Usage count = \\d+"
 		}
 	]
 }