Set default Agent's initial maxSockets to 1

The [new rationale](https://github.com/tessel/runtime/issues/674#issuecomment-66214631) here is that:

- the lower, the better as far as current CC3K stack goes
- this may also make it a little clearer where the problem lies in situations like #674, than the previous value of 2

@LinusU how does this sound as a replacement for #675?