Subscriptions to influxdb not removed cleanly?

@gshif is already working on this.

Since Mar 23, 2018.

When kapacitor starts up it creates subscriptions however it then seems to close the sockets randomly without telling influxdb resulting in connection refused spam in the logs e.g.

```
[subscriber] 2016/08/03 23:25:36 write udp 127.0.1.1:33008: connection refused
```

```
Aug 03 23:11:06 influxdb-1 docker[1836]: [influxdb] 2016/08/03 23:11:06 I! started UDP listener for _internal monitor
Aug 03 23:11:06 influxdb-1 docker[1836]: [udp:telegraf.default] 2016/08/03 23:11:06 I! Started listening on UDP: 172.17.0.3:45678
Aug 03 23:11:06 influxdb-1 docker[1836]: [influxdb] 2016/08/03 23:11:06 I! started UDP listener for telegraf default
Aug 03 23:11:06 influxdb-1 docker[1836]: [udp:servercheck.default] 2016/08/03 23:11:06 I! Started listening on UDP: [::]:33008
Aug 03 23:11:06 influxdb-1 docker[1836]: [influxdb] 2016/08/03 23:11:06 I! started UDP listener for servercheck default
Aug 03 23:11:06 influxdb-1 docker[1836]: [stats] 2016/08/03 23:11:06 I! opened service
Aug 03 23:11:06 influxdb-1 docker[1836]: [httpd] 2016/08/03 23:11:06 I! Starting HTTP service
Aug 03 23:11:06 influxdb-1 docker[1836]: [httpd] 2016/08/03 23:11:06 I! Authentication enabled: false
Aug 03 23:11:06 influxdb-1 docker[1836]: [httpd] 2016/08/03 23:11:06 I! Listening on HTTP: [::]:9092
Aug 03 23:11:06 influxdb-1 docker[1836]: [run] 2016/08/03 23:11:06 I! Listening for signals
```

netstat shows the port for subscription which is working but the other one is missing.

```
netstat -na |grep 45678
udp6 0 0 :::45678 :::*
netstat -na |grep 33008
```

```
show subscriptions
name: servercheck
-----------------
retention_policy name mode destinations
default kapacitor-961a184a-8000-4f74-b68d-9bd6c4e6f1fe ANY [udp://influxdb-1:33008]
```