ensure docker group exists

In the latest docker rpm on fedora28 the
docker group is not created at all.

Change-Id: I79dadf948494e1cb6881a5dfe47669424c2feacb

roles/create-zuul-based-reproducer/templates/reproducer-zuul-based-quickstart.sh.j2

@@ -198,6 +198,9 @@ if ! groups | grep -Eq "docker|dockerroot"; then
         DG=docker
     elif grep -q dockerroot: /etc/group; then
         DG=dockerroot
+    elif ! grep -q docker /etc/group; then
+        sudo groupadd docker
+        DG=docker
     fi
     sudo usermod -aG $DG $USER
     echo -e "\e[31m WARNING: Add user immediately to the $DG group. \
@@ -221,6 +224,9 @@ if [[ -f /etc/docker/daemon.json ]]; then
      fi
 fi
 
+# Ensure the docker process has been restarted
+sudo systemctl restart docker
+
 # Start from a clean workspace
 export WORKSPACE
 mkdir -p $WORKSPACE