fix crashes in cvsyncd now made visible by malloc's junk-after-free default.
From patrick keshishian who says 'I think protocol_exchange() will eventually
"realize" that status and/or error are not ok, and will return false, and
server thread will call assess_done(), which will socket_close() and
config_revoke().' Thanks for looking into this and suggesting the diff.
Survived 24h+ on my server, and looks good to naddy.
a13880e19f