Update docker install to work out of the box (grafana#4163)

- Fix promtail config path
- Name loki container to link networks

Author: smuth4

docs/sources/installation/docker.md

@@ -19,9 +19,9 @@ Copy and paste the commands below into your command line.
 
 ```bash
 wget https://raw.githubusercontent.com/grafana/loki/v2.3.0/cmd/loki/loki-local-config.yaml -O loki-config.yaml
-docker run -v $(pwd):/mnt/config -p 3100:3100 grafana/loki:2.3.0 -config.file=/mnt/config/loki-config.yaml
+docker run --name loki -v $(pwd):/mnt/config -p 3100:3100 grafana/loki:2.3.0 -config.file=/mnt/config/loki-config.yaml
 wget https://raw.githubusercontent.com/grafana/loki/v2.3.0/clients/cmd/promtail/promtail-docker-config.yaml -O promtail-config.yaml
-docker run -v $(pwd):/mnt/config -v /var/log:/var/log grafana/promtail:2.3.0 -config.file=/mnt/config/promtail-config.yaml
+docker run -v $(pwd):/mnt/config -v /var/log:/var/log --link loki grafana/promtail:2.3.0 -config.file=/mnt/config/promtail-config.yaml
 ```
 
 When finished, `loki-config.yaml` and `promtail-config.yaml` are downloaded in the directory you chose. Docker containers are running Loki and Promtail using those config files.
@@ -37,9 +37,9 @@ Copy and paste the commands below into your terminal. Note that you will need to
 ```bash
 cd "<local-path>"
 wget https://raw.githubusercontent.com/grafana/loki/v2.3.0/cmd/loki/loki-local-config.yaml -O loki-config.yaml
-docker run -v <local-path>:/mnt/config -p 3100:3100 grafana/loki:2.3.0 --config.file=/mnt/config/loki-config.yaml
+docker run --name loki -v <local-path>:/mnt/config -p 3100:3100 grafana/loki:2.3.0 --config.file=/mnt/config/loki-config.yaml
 wget https://raw.githubusercontent.com/grafana/loki/v2.3.0/clients/cmd/promtail/promtail-docker-config.yaml -O promtail-config.yaml
-docker run -v <local-path>:/mnt/config -v /var/log:/var/log grafana/promtail:2.3.0 --config.file=/mnt/config/promtail-config.yaml
+docker run -v <local-path>:/mnt/config -v /var/log:/var/log --link loki grafana/promtail:2.3.0 --config.file=/mnt/config/promtail-config.yaml
 ```
 
 When finished, `loki-config.yaml` and `promtail-config.yaml` are downloaded in the directory you chose. Docker containers are running Loki and Promtail using those config files.