Catch and log errors when connecting/ disconnecting signals in node server

I tracked down log messages like this that were appearing in the node logs:

```
2014-12-05 15:40:25-0800 [ServerProtocol,client] ('N', 'o', ' ', 'r', 'e', 'c', 'e', 'i', 'v', 'e', 'r', 's', ' ', 'f', 'o', 'r', ' ', 's', 'i', 'g', 'n', 'a', 'l', ' ', "'", 's', 'e', 'r', 'v', 'e', 'r', '_', 's', 't', 'a', 'r', 't', 'i', 'n', 'g', "'", ' ', 'f', 'r', 'o', 'm', ' ', 's', 'e', 'n', 'd', 'e', 'r', ' ', 'A', 'n', 'y')
```

These were due to an exception being thrown while disconnecting some internal messages inside the node server. These exceptions could in general be ignored, but we'll at least log them.