Fixed steps for starting Docker in Quickstart guide

patch by Sathyanarayanan Saravanamuthu; reviewed by Erick Ramirez for CASSANDRA-17485
Closes #116

site-content/source/modules/ROOT/pages/quickstart.adoc

@@ -39,7 +39,7 @@ A Docker network allows us to access the container's ports without exposing them
 
 [source]
 --
-docker run --name cassandra cassandra
+docker network create cassandra
 
 docker run --rm -d --name cassandra --hostname cassandra --network cassandra cassandra
 --