Add ability to specify cinder lvm_type option

Cinder has had an lvm_type option for quite a while
that allows the LVM driver to be configured to use
thin provisioning.

This required an additional PPA in Precise, but is
available in the default Trusty packages.

This patch adds the lvm_type option, and we'll use
it to do gate testing against the lvm_thin configuration.

Change-Id: I99c7fea131f3d79747ec75052adf8b24f41ba483
diff --git a/lib/cinder_backends/lvm b/lib/cinder_backends/lvm
index 35ad209..411b82c 100644
--- a/lib/cinder_backends/lvm
+++ b/lib/cinder_backends/lvm
@@ -51,6 +51,7 @@
     iniset $CINDER_CONF $be_name volume_driver "cinder.volume.drivers.lvm.LVMVolumeDriver"
     iniset $CINDER_CONF $be_name volume_group $VOLUME_GROUP_NAME-$be_name
     iniset $CINDER_CONF $be_name iscsi_helper "$CINDER_ISCSI_HELPER"
+    iniset $CINDER_CONF $be_name lvm_type "$CINDER_LVM_TYPE"
 
     if [[ "$CINDER_SECURE_DELETE" == "False" ]]; then
         iniset $CINDER_CONF $be_name volume_clear none