subtests..syslog: Add syslog test

To view log messages created in containers on your host system,
mount the /dev/log/ directory on host to all containers,
the container will automatically direct log messages into this directory.

Signed-off-by: Ouyang Guohua <gouyang@redhat.com>
Merge pull request #157 from ouyanggh/guohua

subtests..syslog: Add syslog test