Remove Ubuntu 14.10 as supported distribution

Ubuntu 14.10(utopic) reached end of life[1].

[1]: https://lists.ubuntu.com/archives/ubuntu-announce/2015-July/000197.html

Change-Id: Iab13ca797bda56462d9d117aa500d3ba0d9bebcb
diff --git a/lib/nova_plugins/functions-libvirt b/lib/nova_plugins/functions-libvirt
index 5525cfd..78c5978 100644
--- a/lib/nova_plugins/functions-libvirt
+++ b/lib/nova_plugins/functions-libvirt
@@ -23,7 +23,7 @@
 # Installs required distro-specific libvirt packages.
 function install_libvirt {
     if is_ubuntu; then
-        if is_arch "aarch64" && [[ ${DISTRO} =~ (trusty|utopic) ]]; then
+        if is_arch "aarch64" && [[ ${DISTRO} == "trusty" ]]; then
             install_package qemu-system
         else
             install_package qemu-kvm