Rename DOCKER_HOST to REMOTE_DOCKER_HOST for configuring remote URL

The connection to a remote Docker is performed through the DOCKER_HOST
URL in config.xml. Previously the DOCKER_HOST was clashing with the
local environment, making Docker thinking that also the server needed
to be started remotely.

Rename the variable to REMOTE_DOCKER_HOST to avoid clashes with
the communication with the local Docker daemon. Also, the new
REMOTE_DOCKER_HOST variable is stored into the Jenkins environment
so that the configuration XSLT processor can replace it into the
config.xml and allow Jenkins to start with the proper connectivity
to the remote Docker server.

Change-Id: Ibd40c2cb26148dd946f724cc5ad1c608dccecf11

jenkins-docker/server/Dockerfile

diff --git a/jenkins-docker/server/Dockerfile b/jenkins-docker/server/Dockerfile
index 37cdaea..6ee9bd5 100644
--- a/jenkins-docker/server/Dockerfile
+++ b/jenkins-docker/server/Dockerfile
@@ -41,7 +41,7 @@
 ENV OAUTH_SECRET secret
 ENV JENKINS_API_USER user
 ENV JENKINS_API_PASSWORD pass
-ENV DOCKER_HOST unix:///var/run/docker.sock
+ENV REMOTE_DOCKER_HOST unix:///var/run/docker.sock
 ENV BINTRAY_URL https://dl.bintray.com/lucamilanesio
 
 COPY edit-config.xslt $JENKINS_REF

jenkins-docker/server/Makefile

diff --git a/jenkins-docker/server/Makefile b/jenkins-docker/server/Makefile
index 6cdbce2..96d6572 100644
--- a/jenkins-docker/server/Makefile
+++ b/jenkins-docker/server/Makefile
@@ -18,6 +18,7 @@
 GERRIT_CI_PEM=./tls/gerrit-ci.pem
 UID=1000
 GID=1000
+REMOTE_DOCKER_HOST=unix:///var/run/docker.sock
 # To bump plugin versions:
 # * Make required changes in required_plugins.txt and set PLUGIN_FILE=required_plugins.txt
 # * Run `make start`, check the plugins work using the console
@@ -53,13 +54,14 @@
 
 create_env:
 	printf \
-        "USE_SECURITY=%s\nOAUTH_ID=%s\nOAUTH_SECRET=%s\nJENKINS_API_USER=%s\nJENKINS_API_PASSWORD=%s\nDOCKER_GID=%s\n" \
+        "USE_SECURITY=%s\nOAUTH_ID=%s\nOAUTH_SECRET=%s\nJENKINS_API_USER=%s\nJENKINS_API_PASSWORD=%s\nDOCKER_GID=%s\nREMOTE_DOCKER_HOST=%s\n" \
         "${USE_SECURITY}" \
         "${OAUTH_ID}" \
         "${OAUTH_SECRET}" \
         "${JENKINS_API_USER}" \
         "${JENKINS_API_PASSWORD}" \
-        "${DOCKER_GID}" > jenkins-container.env
+        "${DOCKER_GID}" \
+        "${REMOTE_DOCKER_HOST}" > jenkins-container.env
 
 start_internal: build_internal create_env ${GERRIT_CI_PEM}
 	-docker rm ${NAME_INTERNAL}

jenkins-docker/server/config.sh

diff --git a/jenkins-docker/server/config.sh b/jenkins-docker/server/config.sh
index 1c9657f..3f28d31 100755
--- a/jenkins-docker/server/config.sh
+++ b/jenkins-docker/server/config.sh
@@ -15,7 +15,7 @@
 
 xsltproc \
   --stringparam use-security $USE_SECURITY \
-  --stringparam docker-url $DOCKER_HOST \
+  --stringparam docker-url $REMOTE_DOCKER_HOST \
   --stringparam oauth-client-id $OAUTH_ID \
   --stringparam oauth-client-secret $OAUTH_SECRET \
   $JENKINS_REF/edit-config.xslt $CONFIG > /tmp/config.xml.new