Commit Briefs
add kamictl debug: list open fids on every ongoing connection
while here also fix the imsg retrival loop
add IMSG_CTL_DEBUG to debug the opened fid
meant to be used from kamictl to dump all the opened fid by every connection.
cache listener flags in struct client
this saves us from the small chance that a client accepted before reconf uses the flags from a listener post reconf.
fix restart in listener
drop connections in the handshake phase: the listener from where they've been accepted is now being replaced and its id is no more meaningful. Clients for which we have already sent an auth request are kept.
use serial ids and drop usage of arc4random
it's not so useful here and not (directly) used anywhere else.
listener: correctly swap config after reload
and don't forget to free the current config!