Unfortunately, it *does* set this for containers as well.

Before:
```
bharrington@localhost ~ $ docker run -t -i  --rm busybox /bin/ash
/ # ulimit -n
1024
```

after:
```
bharrington@localhost ~ $ sudo vim /etc/systemd/system/docker.service 
bharrington@localhost ~ $ sudo systemctl daemon-reload
bharrington@localhost ~ $ sudo systemctl restart docker.service
bharrington@localhost ~ $ docker run -t -i  --rm busybox /bin/ash
/ # ulimit -n
1048576
```