Add unallocated_pvs fact to the disk_management module

This change adds a custom fact named 'unallocated_pvs' to the
disk_management module. It returns the array of disk partitions that
are flagged as LVM partitions but not yet configured as physical
volumes by LVM.

Change-Id: I7d7fc5102cc208d95a9de6353f2a37f138026ea5

deployment_scripts/puppet/modules/disk_management/lib/facter/unallocated_pvs.rb

@@ -0,0 +1,24 @@
+# Return the list of LVM disk partition that haven't been allocated yet
+unallocated_pvs = []
+
+# Enumerate disk devices
+devices = Dir.entries('/sys/block/').select do |d|
+    File.exist?( "/sys/block/#{ d }/device" )
+end
+
+devices.each do |device|
+    device = "/dev/#{ device }"
+    # Filter only partitions flagged as LVM
+    lvm_partitions = Facter::Util::Resolution.exec(
+        "parted -s -m #{ device } print 2>/dev/null").scan(/^(\d+):.+:lvm;$/).flatten
+    lvm_partitions.each do |x|
+        # Filter only partitions which haven't been created yet
+        pvs = Facter::Util::Resolution.exec(
+            "pvs --noheadings #{ device }#{ x } 2>/dev/null")
+        if pvs.nil? then
+            unallocated_pvs.push("#{ device }#{ x }")
+        end
+    end
+end
+
+Facter.add("unallocated_pvs") { setcode { unallocated_pvs } }