This probably isn't the best fix, but it seems to make Facebook
connections stable for me.

After applying PR #497 you end up with frequent disconnects with:

```
Failed to read thrift: api.c:1515 fb_api_cb_publish_mst: assertion 'id == 2' failed
```

@.baltitenger said they checked that because that was the value in the
messages they saw, and they didn't know what other values would mean.

It seems messages with a different value don't break things (but we're
probably not handling them properly), but not crashing on them is
certainly better than crashing on them.

Fixes #496

Signed-off-by: Phil Dibowitz <phil@ipom.com>