This modifies pattern for catching cpp problem messages produced by
ABRT. Found that not all mentioned messages fit into former pattern.
For example following is valid cpp problem message produced by ABRT:
Process xxx (bad_binary) crashed in Will::Fail::a() [clone .isra.2]()
but doesn't fit former pattern, since it's last part contains
whitespaces.
* 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.
1) Add lookback support in kernel monitor. After started, Kernel monitor
will check some old logs to detect problems which happened before last
node reboot.
2) Add `lookback` and `startPattern` in kernel monitor configuration.
* `lookback` specifies how long time kernel monitor should look back.
* `startPattern` specifies which log indicates the node is started.
kernel monitor will clear all current node conditions once it finds
a node start log. This makes sure that old problems won't change the
node condition.
3) Add support for kernel panic monitoring, the null pointer and divide
0 kernel panic will be surfaced as event. Usually kernel monitor will
report these events during looking back phase.
