syslog: fixes and updates to rsyslogd and logrotate.
Adjust lograte size to prevent a mismatch.
Change rsyslogd size to be actual size instead of a naive value.
Potentially fix bug #13699000 by increasing the maximum number of TCP sessions.

Rsyslog was rejecting agents from connecting because of MaxSessions, which caused those
agents to go into spirals of trying to restart their rsyslog worker over and over,
which then generated tons of DEBUG level logging on machine-0 because of the workers
restarting, which then spammed the log file a lot.