Now that keepalive.py records HTTP request count and the
number of bytes sent and received as part of performing those
requests, we can easily print a report on the activity when
closing a peer instance!

Exact byte counts are globbed in tests because they are influenced
by non-deterministic things, such as hostnames and port numbers.
Plus, the exact byte count isn't too important anyway.

I feel obliged to note that printing the byte count could have
security implications. e.g. if sending a password via HTTP basic
auth, the length of that password will influence the byte count
and the reporting of the byte count could be a side-channel leak
of the password length. I /think/ this is beyond our threshold
for concern. But if we think it poses a problem, we can teach the
byte count logging code to e.g. ignore sensitive HTTP request
headers. We could also consider not reporting the byte count of
request headers altogether. But since the wire protocol uses HTTP
headers for send...