oeqa/runtime/syslog.py: Improve test_syslog_logger on systemd
When an image uses systemd journald acts as a main syslog daemon using
/dev/log.
The test_syslog_logger try to log a predifined message into the syslog
using logger and then search using grep in /var/log/messages if this
fails for some reason (file rotated) now search the predifined message
into the journal.
Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
