Fix typo: _create_volume_group => _create_lvm_volume_group

Change-Id: Ifb648c9eb4a57ac0fc97afb842e83286789801dd
diff --git a/lib/lvm b/lib/lvm
index 1fe2683..8afd543 100644
--- a/lib/lvm
+++ b/lib/lvm
@@ -78,7 +78,7 @@
 }
 
 
-# _create_volume_group creates default volume group
+# _create_lvm_volume_group creates default volume group
 #
 # Usage: _create_lvm_volume_group() $vg $size
 function _create_lvm_volume_group {