This gets rid of some non-type safe string comparisons and access to members that are implementation details of `class P2PConnection(asyncore.dispatcher)`. Such refactoring is required to replace the deprecated asyncore with something more sane.

Changes:
* Get rid of non-enum member `state` and replace is with bool `connected`
* Get rid of confusing argument `pushbuf` and literally just push to the buffer at the call site