Update Vagrant's Ubuntu box provisioning script

Starting from Vivid Ubuntu uses systemd as the
default boot manager instead of upstart. Updating
the way the docker daemon is configured to follow
the systemd way.
Setting env variable GUNICORN_OPTS=[--preload]
to fix race condition and avoid IntegrityError
when pushing images to local registry

Change-Id: I841f85015c2c3683ef7e1e454ec1369263063c45
Related-bug: https://github.com/docker/docker-registry/issues/518
Closes-Bug: #1523336

dev/vagrant/ubuntu-bootstrap.sh

@@ -25,10 +25,13 @@ EOF
 install_docker() {
     echo "Installing Docker"
     apt-key adv --keyserver hkp://pgp.mit.edu:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
-    echo "deb https://apt.dockerproject.org/repo ubuntu-trusty main" > /etc/apt/sources.list.d/docker.list
+    echo "deb https://apt.dockerproject.org/repo ubuntu-vivid main" > /etc/apt/sources.list.d/docker.list
     apt-get update
     apt-get install -y  docker-engine=1.8.2*
-    sed -i -r "s,^[# ]*DOCKER_OPTS=.+$,DOCKER_OPTS=\"--insecure-registry ${REGISTRY}:${REGISTRY_PORT}\"," /etc/default/docker
+    sed -i -r "s,(ExecStart)=(.+),\1=/usr/bin/docker daemon -H fd:// -H tcp://0.0.0.0:2375 -H unix:///var/run/docker.sock --insecure-registry ${REGISTRY}:${REGISTRY_PORT}," /lib/systemd/system/docker.service
+    systemctl daemon-reload
+    systemctl enable docker
+    systemctl restart docker
 }
 
 install_python_deps() {
@@ -55,8 +58,10 @@ create_registry() {
             -e MIRROR_SOURCE=https://registry-1.docker.io \
             -e MIRROR_SOURCE_INDEX=https://index.docker.io \
             -e STORAGE_PATH=/var/lib/registry \
+            -e GUNICORN_OPTS=[--preload] \
+            -e SEARCH_BACKEND=sqlalchemy \
             -v /data/host/registry-storage:/var/lib/registry \
-            registry
+            registry:0.9.1
 }
 
 configure_kolla() {