Currently we don't have any logs from our gitea sshd processes because
sshd logs to syslog by default and /dev/log isn't in our containers. You
can ask sshd nicely to log to stderr instead with the -e flag which
docker will pick up and store for us.
Update the sshd command to include -e then use testinfra to check we
collect logs and they are accssible from docker.
Change-Id: Ib7d6d405554c3c30be410bc08c6fee7d4363b096
05e0ffdebc