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 b/lib/cinder
index eb0e1d7..93285bf 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -65,6 +65,10 @@
 CINDER_SERVICE_PORT_INT=${CINDER_SERVICE_PORT_INT:-18776}
 CINDER_SERVICE_PROTOCOL=${CINDER_SERVICE_PROTOCOL:-$SERVICE_PROTOCOL}
 
+# What type of LVM device should Cinder use for LVM backend
+# Defaults to default, which is thick, the other valid choice
+# is thin, which as the name implies utilizes lvm thin provisioning.
+CINDER_LVM_TYPE=${CINDER_LVM_TYPE:-default}
 
 # Default backends
 # The backend format is type:name where type is one of the supported backend