Transitioning to a new Call Collect mode.

Currently we were copying code from cf-hub into cf-serverd to do the
query. This led to some problems regarding both synchronization and
code understandability.
The new approach is to share the connection received by cf-serverd with
cf-hub and let cf-hub add the connection to its internal queue. That way
cf-hub will take ownership of the connection and query the agent at its own
convenience.