Add is_ubuntu function

This replaces all of the [[ "$os_PACKAGE" = "deb" ]] tests, except when
those tests are before straight calls to dpkg.

Change-Id: I8a3ebf1b1bc5a55d736f9258d5ba1d24dabf04ea
diff --git a/lib/nova b/lib/nova
index 6445a07..970806d 100644
--- a/lib/nova
+++ b/lib/nova
@@ -202,7 +202,7 @@
         # splitting a system into many smaller parts.  LXC uses cgroups and chroot
         # to simulate multiple systems.
         if [[ "$LIBVIRT_TYPE" == "lxc" ]]; then
-            if [[ "$os_PACKAGE" = "deb" ]]; then
+            if is_ubuntu; then
                 if [[ ! "$DISTRO" > natty ]]; then
                     cgline="none /cgroup cgroup cpuacct,memory,devices,cpu,freezer,blkio 0 0"
                     sudo mkdir -p /cgroup
@@ -228,7 +228,7 @@
 EOF
         fi
 
-        if [[ "$os_PACKAGE" = "deb" ]]; then
+        if is_ubuntu; then
             LIBVIRT_DAEMON=libvirt-bin
         else
             # http://wiki.libvirt.org/page/SSHPolicyKitSetup
@@ -393,7 +393,7 @@
 # install_nova() - Collect source and prepare
 function install_nova() {
     if is_service_enabled n-cpu; then
-        if [[ "$os_PACKAGE" = "deb" ]]; then
+        if is_ubuntu; then
             LIBVIRT_PKG_NAME=libvirt-bin
         else
             LIBVIRT_PKG_NAME=libvirt
@@ -403,7 +403,7 @@
         # splitting a system into many smaller parts.  LXC uses cgroups and chroot
         # to simulate multiple systems.
         if [[ "$LIBVIRT_TYPE" == "lxc" ]]; then
-            if [[ "$os_PACKAGE" = "deb" ]]; then
+            if is_ubuntu; then
                 if [[ "$DISTRO" > natty ]]; then
                     install_package cgroup-lite
                 fi