Make heka collect libvirtd.log in nova_libvirt container

Test results of this patch set are at:
http://paste.openstack.org/show/491382/

Change-Id: I1bc8bdb3180f30dc69af28a35fa057ac801bde0f
Closes-Bug: #1560298

docker/nova/nova-libvirt/extend_start.sh

@@ -12,3 +12,10 @@ fi
 if [[ $(lsmod | grep xenfs) ]]; then
     mount -t xenfs xenfs /proc/xen
 fi
+
+if [[ ! -d "/var/log/kolla/libvirt" ]]; then
+    mkdir -p /var/log/kolla/libvirt
+fi
+if [[ $(stat -c %a /var/log/kolla/libvirt) != "755" ]]; then
+    chmod 755 /var/log/kolla/libvirt
+fi