Pin version of LXD to latest LTS, and pin juju 2.8.11

Change-Id: I31f5540e0d8991006e8b3767a94fe4126945cafb
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/installers/full_install_osm.sh b/installers/full_install_osm.sh
index 70b9dca..941e51e 100755
--- a/installers/full_install_osm.sh
+++ b/installers/full_install_osm.sh
@@ -293,7 +293,7 @@
 
     # Install LXD snap
     sudo apt-get remove --purge -y liblxc1 lxc-common lxcfs lxd lxd-client
-    sudo snap install lxd
+    sudo snap install lxd --channel $LXD_VERSION/stable
 
     # Configure LXD
     sudo usermod -a -G lxd `whoami`
@@ -447,7 +447,7 @@
 
 function install_juju() {
     echo "Installing juju"
-    sudo snap install juju --classic --channel=2.8/stable
+    sudo snap install juju --classic --channel=$JUJU_VERSION/stable
     [[ ":$PATH": != *":/snap/bin:"* ]] && PATH="/snap/bin:${PATH}"
     update_juju_images
     echo "Finished installation of juju"
@@ -1575,6 +1575,8 @@
     DOCKER_REGISTRY_URL=$(echo "$DOCKER_REGISTRY_URL" | awk '{split($1,a,"@"); print a[2]}')
 }
 
+LXD_VERSION=4.0
+JUJU_VERSION=2.8
 JUJU_AGENT_VERSION=2.8.8
 UNINSTALL=""
 DEVELOP=""