Configures rsyslog to listen on /rsyslog/imuxsock
Configures rsyslog to listen on /rsyslog/imuxsock

Working with /dev and /dev/log posed a few issues relating to the way
docker initialises. So this change would make imuxsock module listen on
an additional socket which then can be exposed to other containers.

redmatter/docker-rsyslog,redmatter/docker-rsyslog