Related: rhbz#1369439
Keep it same as in RHEL 7.2. They increase the size of the /tmp/syslog file
from ~280K to ~1M, and can be obtained from journal if needed.
Resolves: rhbz#1369439
Rsyslogd used to read messages from /dev/log together with systemd-journald
which resulted in NetworkManager messages not being passed to syslog due to a
race condition during starting NetworkManager and rsyslogd service. So use
imjournal rsyslog plugin that picks messages from journald instead of using the
/dev/log socket. Same as regular RHEL 7 system.
