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

@@ -1,23 +1,32 @@
 #!/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
 
-docker_version=17
-if ! [[ "$(docker --version)" == "Docker version $docker_version"* ]]; then
-    version="$(apt-cache madison docker-ce | cut -f 2 -d \| | grep "$docker_version" | head -n 1 | xargs echo)"
-    ## DOWNGRADE to 17.xx because 18.xx do not support registry v1
-    apt-get install -y --force-yes docker-ce="$version"
-    need_restart=true
-fi
 
-if [ "$need_restart" ]; then
-    systemctl daemon-reload &&
-        service docker restart
+if [ -n "$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 "$docker_version" |
+                       head -n 1 | xargs echo)"
+        ## DOWNGRADE to 17.xx because 18.xx do not support registry v1
+        apt-get install -y --force-yes docker-ce="$version"
+        need_restart=true
+    fi
+
+    if [ "$need_restart" ]; then
+        systemctl daemon-reload &&
+            service docker restart
+    fi
 fi