添加对节点状态的变更的一个事件处理流程

[Ashlee1994]

需要添加一个对节点状态变更的修改功能，以及将对节点状态变更信息存储到数据库中。

需要实现以下功能：

1. 修改节点状态，如果节点状态改为drain或者down之后，不会有任务提交到该节点
2. 恢复节点状态，节点可以恢复为idle状态，重新进入任务资源池，可以运行任务
3. 查看节点不可以运行作业的原因，在drain，down状态下不可以运行作业，显示原因

具体修改方式参考下图：

[Ashlee1994]

需要在目前系统中创建一个event表，可以参考slurm表格设计：

slurm event_table： 记录集群节点事件信息
{ "time_start", "bigint unsigned not null" }, Start of period
{ "time_end", "bigint unsigned default 0 not null" }, End of period
{ "node_name", "tinytext default '' not null" }, Name of node (only set in a node event)
{ "cluster_nodes", "text not null default ''" }, node list in cluster during time period (only set in a cluster event)
{ "reason", "tinytext not null" }, reason node is in state during time period (only set in a node event)
{ "reason_uid", "int unsigned default 0xfffffffe not null" }, uid of that who set the reason
{ "state", "int unsigned default 0 not null" }, State of node during time period (only set in a node event)
{ "tres", "text not null default ''" }, TRES touched by this event

通过sacctmgr show event指令可以查看系统历史所有event信息：