add sudo in front of group add

otherwise fails in some scenarios

docs/operators/tutorial.md

@@ -55,7 +55,7 @@ Abra can't deploy any applications in future steps unless it can run `docker` co
 groups | grep docker
 
 # if the docker group doesn't already exist, add it manually
-groupadd docker
+sudo groupadd docker
 
 # add user to docker group
 sudo usermod -aG docker $USER