fix: [docker-host] don't touch an already installed version of docker

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

precise/host/hooks/install.d/60-docker.sh

@@ -1,17 +1,25 @@
 #!/bin/bash
 
-need_restart=
+
+just_installed=
 if ! type -p docker; then
     echo "Installing docker..."
     type -p curl >dev/null ||
         apt-get install -y curl </dev/null
 
-    curl -sSL https://get.docker.io | sh
+    curl -sSL https://get.docker.io | sh || exit 1
+    just_installed=1
 fi
 
+
+if [ -n "$just_installed" ]; then
+    need_restart=
     docker_version=17
     if ! [[ "$(docker --version)" == "Docker version $docker_version"* ]]; then
-    version="$(apt-cache madison docker-ce | cut -f 2 -d \| | grep "$docker_version" | head -n 1 | xargs echo)"
+        version="$(apt-cache madison docker-ce |
+                       cut -f 2 -d \| |
+                       grep "$docker_version" |
+                       head -n 1 | xargs echo)"
         ## DOWNGRADE to 17.xx because 18.xx do not support registry v1
         apt-get install -y --force-yes docker-ce="$version"
         need_restart=true
@@ -21,3 +29,4 @@ if [ "$need_restart" ]; then
         systemctl daemon-reload &&
             service docker restart
     fi
+fi