docker-sonic-vs doesn't have the infra needed for the syslog rate limit
configuration, so it's not going to be rendering jinja templates to
overwrite /etc/rsyslog.conf. This also means that syslog messages would
get logged twice (because both the default /etc/rsyslog.conf file and
/etc/rsyslog.d/50-default.conf are telling it to log to syslog).
Therefore, keep the custom static /etc/rsyslog.conf file for docker-sonic-vs.
Fixessonic-net/sonic-swss#2570.
Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>